Some parts (like legs and shoulders) are shaded, so eyes expect that other parts will follow the same 'rules' and will be shaded too.
@ A.B. Lazer - I was going more for an anime feel, so the shading should be looked at in terms of anime-characters (Which rarely have any shading on their bellies). Thanks for your advice, though! I'll work on the arms ;)
Looks quite nice. But hands are too small, arms have no joints and muscles - at this resolution they should be evident so arms should not be so straight. Also shading under belly and ribs is missing as well as the nose. Also pants should be shaded as continuation of body with minor details to show that it is fabric - now they look like somebody blew them up.
The head are too small too. Work more on the anatomy.