I like the designs, especially the last one. The faces are well constructed, they give good detail with few pixels. As far as what can be improved, I see three things. First, there is not enough contrast, especially between the skin tones. This makes the facial details hard to read unless you zoom in. Second, the body proportions are off. Legs should be about half the height of the body. Third, the pose of the legs does not have the level of quality as the rest of the stuff. Both legs are perfect cylinders, at weird angles. You have a lot of room to sculpt the shape of the leg even at this resolution. Don't settle for angled cylinders. Here is an edit that tries to address these three things.
A few other things I did:
- Widen his torso by one pixel
- Eliminate some redundant colors
