The selout to black is far too harsh.
The back of the head looks very flat. This might be remedied with a hilight or some hair.
The back in general looks flat. It's as though you have the lightsource rotating along with him so it stays in front of him. That doesn't make much sense in a game world. For the straight-on views, I think his feet could be moved 1px apart. The front-facing diagonal looks like he's leaning/about to fall over sideways. Try making the far leg straight.
Nice, though. Keep it up.