EDIT: How terribly stupid of me, I didn't notice you were primarily asking about the teeth. Fixed my version with a suggestion on how to do the teeth.

I'm not very experienced myself, but I would recommend using more of the second-darkest color, try to keep dithering to a minimum and use bigger groups/clusters of pixels.

Here's a very quick edit

Oh, I did read about that. I just couldn't put two and two together, I guess. I did find it fascinating, and it seems every bit as useful-yet-non-intuitive as a number of other pixel art axioms, trends, doctrines, or whatever you want to call them.

I do think certain that tutorials in many ways define the pixel art community. For example, Cure, you've written one of the most comprehensive, widely referenced pixel art tutorials that I've come across. And it's helped me a lot. But it's interesting to see that it seems to influence a lot of new pixel artists, or at least correlate with the problems they're having. Thanks to your tutorial, most people who are new to pixel art tend to avoid the obvious jaggies, banding and pillow shading. But they seem to make the same mistakes with dithering, and I can't help but wonder if this is because dithering is brought up relatively early in your tutorial, and makes up a substantial portion of it. I've no idea if it is indeed because of your tutorial, I've just noticed that a lot of new pixel artists approach dithering as if it were mandatory.

And most of the other criticism that meets new pixel artists is stuff that isn't directly covered in your tutorial, because it's usually not specific to pixel art. It's stuff like composition, color theory, anatomy, perspective, etc. that people can and should learn elsewhere. But then they don't, often because they seem to think that pixel art is a free pass to making cool art without knowing how to paint. Oops, a little rant. Sorry. [Just to clarify, I'm not suggesting that your tutorial needs to cover everything, I'm just reflecting on the impact of your tutorial.]

In any community, there's going to be two camps - one which is willing to bend over backwards to help potential newcomers, and others who take the Mr. Miyagi approach and prefer to let newcomers do their own research and prove themselves. And most people fall somewhere in between, of course. But I think that helping members find the right tutorials with the right content has a huge impact. Perhaps in a few years, when I have a bit more knowledge, I will try to help with this.

TL;DR: The impact of any sort of trend or "rule" probably depends on two things: the degree to which it is used and mentioned by the most popular artists in the community, and the way it is described in tutorials.

I enjoy discussions like this one. It's interesting to see people wrestle with their own artistic preferences and try to justify them rationally. But on a rational level, I agree with NaCl, that the study of mastering individual pixels is a logical choice when working with any medium consisting ultimately of individual pixels. Indeed, I imagine that the ultimate closing of the circle, at present, would be if rendering software was able, somehow, to emulate the extremely complex process of pixel art. Imagine if every frame in a game of Grand Theft Auto or Quake Arena was essentially pixel art. But then, that will probably never happen, just like we will never see the iBeeper or a blu-ray compatible laser disc player.

Mr. Beast: I don't think you need to have been alive for nostalgia to play a role. I get a great deal of nostalgia from various 1950's, 1960's and 1970's peculiarities. And I was born in the 1980's.

Pixel art is such a vast category of art that I don't believe there are anyone who are turned off by it. There is pixel art out there that you wouldn't know was pixel art, unless someone told you or you were an experienced pixel artists yourself. A lot of pixel artists strive to make their art look like it was photoshopped, or even taken as a picture. I think it's more about the style, rather than the method. There are 3D FPS that I really love and others that I really hate, simply due to their artistic style. I like 3D games, I love Super Mario, but I hate the style of almost every Mario Game they've made since Nintendo 64 came out. Low resolution pixel art isn't for everyone, but neither is low poly-count 3D games.

@ Ellian: Nice link, thanks for that! It comes as no surprise that the French are doing their part, given their history of animation and comics. A lot of stuff there that I haven't seen before.

@ Helm: Thanks for the explanation. And I had the same impression in regards to C64 art as well. In regards to pushing the envelope, who would you say has pushed the envelope in recent years? Say since 2010? It looks like people are getting better at working with the "rules" of pixel art, but in terms of experimenting in new directions and paving way for the future? I guess that there's only so much you can do with a given medium. But I can't help but think that there's a lot of potential in looping animations that you can do better with pixel art than any other art form, and it's something that people haven't fully tapped into yet, as far as I can tell. I'm not talking about simple running sprites, I'm talking about portraits, landscapes, complex scenes, abstract pixel art, etc. Especially on a large canvas, with the amount of detail that pixel art allows. And of course, not just sparkling lights, eyes blinking and flickering candles. I mean something more... substantial.

I'm not sure I follow in regards to the no single pixel thing. Do you mean your stance in regards to the freehand tool vs drawing with lines? If you could expand on the last paragraph in your post, that would be very nice.
EDIT: Never mind, found the answer in the latest cluster study thread. But I'm still confused why you feel skeptical. Is it a matter of having such a "refined taste" that your criteria are impossibly hard for other people to appreciate and conform to?

@ Mr. Fahrenheit: I would have loved something like that when I was younger, before I got into Warhammer 40,000 and stuff like that. Thanks for the suggestion.

@ Vagrant: Cheers! I'm not so interested in sprites personally, but it's very good to know!

Give it a few weeks, you'll snap out of a pixelling trance after going 16 hours straight, empty pizza and chinese food boxes littering the room, cat trying to claw its way through the walls to find a new owner, while you barely recognise the sound of the police knocking on the door, with complaints of weird smells coming from your apartment.

Anyway, nice first attempt. Here's a few pointers:

1) Start smaller. Smaller pieces force you to work harder with pixel control, while being much easier to modify and improve as you get feedback and learn new things.
2) Decide what the light source is and then think how it applies to every surface. For example, the top of this furniture is the exact same shade as the shelves underneath. If the light source is above the cupboard, then the shelves should be at least partially in shadow, if not fully. Not only are these surfaces the same colour right now, but the fact that the shelves have dark panels on both sides, while the top of the cupboard is surrounded by retina-burning bright yellow walls, actually creates the illusion that the shelves are brighter than the top of the cupboard! Which would be weird.
3) Also notice how the vertical panels in the cupboard are equally outside as inside.
4) Be consistent about how you draw outlines and edges. The top shelf has a dark edge on top, while the shelf below has a bright edge on top. The right side of the cupboard is brighter than the left side of the cupboard, but the left side has a brighter edge on top. Also, your book has dark edges and outlines on all sides.
5) Please wait more than a few hours before bumping your thread 

Here's an ancient chinese story about pixel art.

Once upon a time, a young orphan went to the Shaolin Temple and asked to see the Abbot.
When the young boy came before the Abbot, he knelt down and said: “Honourable Master, would you please accept me as your student and teach me Kung Fu? I will follow your instruction and serve you anyway I can, and I promise I won’t let you down.”

The Abbot decided to put the young boy through a test to see whether he was suitable or not as a student, so he said to the young boy: “Of course I will teach you Kung Fu, but since I am about to be away for one year to take care of some monastic business in some far away provinces, could you do something for me in my absence?” The young boy was so pleased he had the chance to serve the Abbot that he readily agreed to the request.

The Abbot took the young boy to the nearby forest and pointed to a big tree: “Could you cut down that tree and use it to carve a Buddha statue for me?” The boy quickly replied: “This I will gladly do, Honourable Master. I promise the statue will be ready upon your return.”

Next day, as soon as the Abbot left the monastery, the young boy went to the forest and chopped down the tree with an axe and proceeded to make a statue of Buddha with it. Determined to please the Abbot, he worked with his best effort to make a fine carving of it.

By the time the Abbot returned to the monastery a year later, the young boy had completed the carving of a five feet tall Buddha statue and was eager to present his pride and joy to the Abbot. Having examined the Buddha statue closely the Abbot decided to give the young boy a further test. “The workmanship of this statue is very good but it isn’t what I was expecting. I need a statue smaller than this. Since I am due to be away for another year, could you use the time to make this Buddha statue smaller for me?”

On hearing this, the young boy was very disappointed but none the less agreed reluctantly to make the statue smaller. Besieged by the lack of appreciation and unhappiness, the young boy found he had to force himself to work. Six months on, he was shocked to realise he had carved an ungainly looking Buddha with a crooked, unhappy face.

The boy was so depressed with what he had done that he could not bring himself to work any further and ceased all work on the statue. Days passed into weeks and weeks into months, the Abbot was due to return shortly, and the boy felt the Abbot would surely reject him as a student for his lack of effort. The more he thought about it, the unhappier he became.

Awakening with a start one morning, he came upon the sudden realisation that if he truly wished to become a student of the Abbot, he must do his best to bring true his promise to the Abbot. Otherwise, why should the Abbot accept him as a student? If completing the carving of the Buddha is what it takes to please the Abbot, then he should put in his best effort and learn to enjoy what he had to do instead of wallowing in resentment.

The change of his perspective proved to be the turning point he needed. He became happier and with newfound patience and determination, he went back to work on the statue. In spite of the shortness of time, the boy managed to reduce the size of the Buddha to two feet tall with a smiling face, by the time the Abbot returned.

The Abbot was pleased with what he saw but decided to give one final test to the young boy. “You did a splendid job but the statue is still a bit too big for what I need,” said the Abbot. “It just so happens that I am due to journey to another monastery in a few days time to give teaching for one year, could you possibly make the statue even smaller while I am away?”

This time, the young boy showed no sign of disappointment for he had learned the importance of patience through having conquered himself. So he answered joyfully: “Honourable Master, I will do exactly as you said.”

For the next twelve months, the young boy spent every available moment he had to refine the carving of the Buddha. The face of the Buddha became increasingly lifelike as it reflected more and more the joy and loving care the boy brought to his work.

By the time the Buddha was refined to a two inches tall statue, the Abbot had once again made his way back to the monastery. Upon seeing what the young boy had done with the statue, the Abbot knew for sure that this young boy had passed the test and would made a good student. The young boy went on to fulfil the high hope of his master and became one of the best students in the Shaolin Temple.