Im going to post a tad against the grain. Not touching lurch here, because the rest of the critique on him is pretty dead on, but the monkey SHOULD keep his overly human face. I think it really adds to the sense that he's not to happy to be a monkey (by making him look sort of like a man in a monkey suite) and I dont particularly think the chest needs to pop more then it already does. I do however, think that the chest needs to have the same light source as the rest of the monkey. The face, currently, is lit from the right side, pretty much straight on, giving it a nice cell shaded look. Although this is theoretically wrong for game sprites (when you flip it, the shading will also flip, thus the standard is top lit,) it looks really good on the monkey. The problem, is his chest is lit from the top right near as I can tell, and as of such does not look like part of the same piece.
Other then that, my only real critique is that the blue fur stands out a bit tooo much, basically coming across as negative space. That could look cool, with the right background, but you might want to consider adding in another shade or two of blue to define the shape of the body a bit.
