This looks a lot better! (great tutorial by the way, really great)
But still, it seems to me like you have only followed the first two arrows. The leaves are added in the last two steps, so you have another 2 arrows to follow.
Here are some more comments:
Where does the light come from?
Why black pixels in the art and why exactly there?
I think your highlights are too dark.
You use large areas without dithering. (This is no problem right now, follow the arrows and the dithering will come).
Why the random lines of pixels coming out of your tree? They look random and rushed, not natural and leave-y.

I know how you feel. I've been in a similar situation like you for years. I can only assume that it's the same for artists (I wake to find myself on the coding side quite often).

The problem is that people either want to do their own pet projects or work for money, but not be a partner in a project they don't deeply care about. The solution is of course to make people interested in your work and then give them the possibility to help you - but how to get someone interested in your work if you can't really start? You basically need to have some $$$ and pay someone for a couple of months, and no artist nor game designer nor programmer can really do that.

Of course you can always use some freely available material to create a demo. But without solid graphics, many people who could help you will not even try the demo. As an artist, you can do mockups, and I think those are great at attracting people. But at least we're no musicians. ("Look at this awesome piece of music I made, let's make it into a game" - ever heard that one? no? me neither. And that's although music pays for half the atmosphere...).

Maybe you need to have a peer group with artists and programmers, connected in real life, in order to start something. And then you can attract people.


Anyhow, back to topic. Did I understand you correctly: What you're asking for is not a full-time artist sitting by your side, rather than an extensive graphics library including free files from the artists at this site. Old stuff they drew and never used, things like that.
It would sure be great to have a "resources" forum, tagged by size, perspective, type (tileset, character, enemy, ...) and license. Something like what we had for warcraft 3: http://www.wc3c.net/resources.php .
I think that's a good idea. It's good for artists so they can look at stuff and learn, and it's good for programmers so they can build games with that stuff. It worked wonders for warcraft III (which also had a good amount of standard graphics, that was a huge bonus!)

Okay brace yourself for some harsh critique. I'm not a master myself so some of this might be nonsense, but you should see for yourself.

I'd try this:
Add some shading... Make one arm darker and dither the torso.
His arms look great when he's walking down, but seem to hardly move in the other direction.
Due to the way his head tilts forward while moving up, it looks like he's moving backwards. The torso should be in front of the head, not the other way round.
Use colors (one pixel or something) to show which arm is behind, which one is in the front.

It's interesting to see a nose with this character size. It makes the hero look young and droll I think, but that's just my feel.
I agree on the hair being a problem, especially when facing up: The shading makes it look kinda wormlike, especially the strand on the top left. In fact, the thing to his right ear shouldn't be divided from the rest of his hair when looking up. The reason it is divided when he's looking down is because hair != face.
I don't see a pattern behind the shading in the hair. I think there should always be some reason to have a shade, like distance, light, or just manipulating an area into one direction or another.
You could try and make the hair move while walking, too.

I'm not sure if I agree with that missing black pixel in the right-foot-forward-going-down frame.

Have you looked at an animated version? The walking animation might look strange due to the fact that the feet are basically a box with a diagonal in it which is jumping from side to side.

As for the facing left and -right versions, I suggest playing with outlines between hair and face. No idea what might happen then.
I recommend looking in detail at these walking frames, too. They seem jumpy. Also: left arm right foot, right arm left foot!
Then you'll notice the reason you put his head one pixel down in the walk-forward frames is because he's actually tilting towards the camera, not because he suddenly became smaller.
So in your walking frames, you should make him more diagonal and make his head stick forward, not down!

PS of some sort: Read the tutorial again and try to remake some of the other examples he shows (like the FF characters), outline by outline, flat color by flat color, shading by shading. Whenever you add a pixel or don't add a pixel, think about why the artist added that pixel or left it out.
Then when you work on your own art, think about every pixel you add or remove. Because in 16x24 (?), every. pixel. counts. ;)

Okay, critique over.
Kind regards, Jonas
PPS: I recognized the hair and was giggling a bit because I read the tutorial myself two days ago. It really helped me get my first pixels on the screen :)

EDIT: yaay! big trees! (I was sloppy when adding the trees to the map, so they don't look perfect... I still need some advice concerning how to place the trees.

Love the simple black-and-white!

Thanks, me too!

I don't have any suggestions for specific tile changes right now, but the structure on the right - is that meant to be a house or ruins? Right now it just looks like a wall.

It is a wall : ) It's supposed to be ruins. Can you tell me which version of the picture you're talking about? I worked on the ruins and I feel the newer version is better, so if you're talking about the old version (simple wall, and to the right of it is some sort of triangle-ish wall) please take a look at the new version (first post, has two wall fragments to the right not just one) and tell me if it's easier to see now.
I'm currently working on larger trees, then come back.
EDIT: the tree looks good, except maybe for the fact that the light is coming from the wrong direction -.-