Gonna try spriting

[StarSock64]

I think that's a bit better.

There's some banding in places
http://www.pixel.schlet.net/#C2
Try to get rid of it

The face/eyes are quite low considering how much head space is on top. I'd either move the face up or shrink the head down a little bit. Or maybe both, I guess it just depends on what looks best.
I'd like to see you play with your colors too. Everything's so desaturated. Try to see what types of colors games use or something.
The closer sleeve seems significantly wider than the other, and I don't think any amount of perspective can account for that much of a difference. By wider, I mean how much the sleeve droops down. It might be easier to see if you temporarily remove the tail.