his right ankle/heel is looking odd, so is his crotch. and he doesn't have hands, just blobs =o. you should at least suggest fingers in the lineart phase, so you're not stumped later.

I don't think gravity would allow for that pose, it's very good for a second pixel art piece.

uHH...

Your shading is everywhere.
It doesn't seem like you have one primary light source.
On the front of the face there is shade yet on his leg it is highlighted.

Omg dude, the concept drawing is the shizz! I think you should pixel the same pose of that in say, half the size.

But ignoring that, i feel that now it seems as if there's an imaginary light-blocking wall between his legs. And at the moment, because the upper half of his leg (above the knee) is flatter and higher, it should catch the light differently than the shin, as now it seems that the leg is generally small. I'm also not so keen on the dithering, as it is very contrasted and so makes the image seem very rough in places. Anyways, keep at it.

~