i wanted to see a demonic pizza and didn't though of a demon eating a pizza.

as for shading:
think of the overall light source and apply the light from one side and keep the other side dark.
stay consistent with the light direction until you get into additional theories for lights and shadows like bouncing lights.
the veins are to much in his eyes. better make some shadows

for the form:
don't forget stuff like lips.
the lower lip of a male is quite big.