Not too shabby, Blue. I'd make a small suggestion that will help bump the piece forward a bit, though. You currently have several different light sources. (One from above, one from the upper back left, one from a slightly lower angle on the left, and the glowing skull/hand.) Unify your light sources -- pick a definitive one or two, then make sure all your subsequent rendering follows them. By having several different light sources, it's causing you to do what's called 'pillow shading' in some spots (along edges is mostly shadow, then the center of each object has the main highlight -- called so because it creates a sort of soft/pillowy lighting feel, which makes shapes harder to read).
Now, since this piece is about a necromancer, I'd push the main light source to be the magic that's emanating from the skull/hand areas. It'll help to reinforce the subject matter of the piece, as well as add some interest/drama.
I did a quick paint over to show you:
See how the magic becomes a major focus and it helps to make the figure feel more solidly defined? By deciding that's your main light source, it lets you add in more descriptive shadows to help round out the figure a bit more. See how things start to pop out/feel more 3D? If you try to push your light source a bit more in this piece, I think it you could get some really cool results! (Or you can file the info away to experiment with on future pieces. Or you can ignore me altogether, which is fine, too. XD)