TSG's Sprites

[Speed-X]

The darkest brown in the mammalian-like creature could use a lot more contrast from the shade of brown before it. Badly.

Also, I don't know if this will help to a drastic extent, but try this when you get the time: instead of starting with the outlines, start by blocking in the
main shape and sculpt it out. This tutorial page goes through this in detail:
http://finalbossblues.com/form-and-light/
I also highly encourage anyone else to go through all of this guy's tutorial if they haven't read it already.

While starting with the outline may just be your thing...you never know! Try something new. You may be surprised.