I'm at work, on an 8 hour shift, in front of a computer and saying I have little to do is an understatement... That said, I apologize if you don't like edits... also, apologies in advance if this sounds harsh or pompous. I don't mean it to be. I whole-heartedly encourage anyone trying to get into pixel art, and hope only to offer some help here.
**Keep in mind, anything marked with a "*" is based on personal preference and should be taken with a boulder of salt**
Here are a few major points that I edited (in no specific order): Line art, colour count, anatomy, palette*, pillow shading, contrast.
Line Art: The general form seemed messy, and as such the shape of the skull was distorted. Instead of appearing round, it looked jagged and almost pointy. I smoothed out the countours to give it a cleaner, more rounded shape. I added AA (both exterior and interior) afterwards to make it appear even more smooth.
Colour count/Contrast: This was the next thing. In your original, I counted 11 shades, many of which were nearly identical. I managed to lower the count to 7 with little loss of detail. I blended the colours together by dithering as opposed to adding new shades. The contrast was rather low as well (which lead to the similarities between certain shades), and I think I upped it (low contrast generally gives an image a 'flat' appearance).
Anatomy: I changed certain features, which may or may not have been stylistic choices. The eyes, for example, I rounded; The 'nostrils', I merged; I added more pronounced separation of the teeth, and, as mentioned rounded the cranium. There are some other, minor things which I can't think of or explain, really, but examine the image and they'll probably pop out...
Pillow Shading: Again, I think it arose from the low contrast/high colour count. It's especially apparent around the eyes/nose, and on the top of the cranium. I think the dietary helps counter this to an extent, but I'm not sure. Anyway, general rule of thumb is pillowing=bad.
Pallete/other*: I altered the palette, as I usually find pure grey to be a bit bland. The pallete I chose was selected for no specific reason, other than that I like it. Other preference based changed include the outline, the outer AA and.. some oater things which I can't pick out or remember... sorry... Anyway, point is, I changed much of the style here, and it should be ignored. The technical stuff (AA, dithering, colourcount, etc.) is what I meant to focus on. My editing just gets a bit carried away by times...
I'm uncomfortable giving seemingly harsh/detailed crits, andalways feel like I sounds like a dink when I do. I'm sorry, again, if I do. I hope there's some good stuff in here, though, and I think it needs to be said that my edit is more eloquent than I am, as it were. Study the picture to see what I mean, 'cause my words are probably garbled and rambling.
Keep pixelling, too! Like I said, I encourage everyone to get into it if they want to, and I'd like to see more from you!
