I'll echo what Corsair said about the contrast; there is not enough of it.
The legs are very short on comparison to the rest of the body, I suggest you increase the length of them by a few pixels; and to shade them, I would say that because the upper legs(don't know what they're called
) are thicker than the forelegs(?) the fabric would be tighter above the knee, and looser below it. I usually shade the foreleg(?) with a shade just darker than the shade I use for the upper leg; then, to make sure that it doesn't look like he's squatting, I would add the lighter color used on the upper leg in a sort of cone shape, with the point facing the knee. This could be hard to nail down with such a small sprite; it would help a lot to study pant-legs in real life, studies like that are probably the best teachers for things like this; much better than me, that's for sure.
If you need more clarification, I'll make an edit in a few days when I get back home.
