it looks quite nice to me, but since you ask for suggestions:
i think the hair should be broken up into lumps, not dithered, since the sprite is so small
the darkest gray could be replaced by the lighter brown to make for a warmer pants tone and to free up anothre color slot
the same light brown could be used to frame the chin which at the moment is difficult to distinguish
the nose, which is clearly separate in the render, could use an outline. he looks very normal here
if you want, take the lightest colro and gve him that bucktooth
