Well dude, i'll be honest with you. It looks more like skinning than painting. Much better than my first coloring job though o/.
The blue ball isn't the only source of light, unless it is dark, and on your pic, it doesn't look dark. You must pick where the other lightsource will be, and make the ball + that clash, which in turn makes more shadows.
Also, unless im mistaken, I see perhaps one, two, possible three painting colors. It shows up good, but I'd paint with at least 4 colors.
Plus, the body makes shadows as well as the light sources.
I'm no professional though, and I could be wrong on all of those points. But i r only tryeh to helpeh!