On the tecnique you use I have very little to say, since it's really well made; maybe I would have prefered abit more of shading on some parts.
Just pay attention at his legs; they don't seem well proportioned with the rest of the body, and their position doesn't match the pose. But it's really light and hard to spot.

On the creative side, I would say that you did a great character. The headpiece that he has, adding the two horns coming out, is an fairly original touch.
I would just suggest you to remove the skull on his left shoulder since there is already one on his belt and it's abit out of context compared to the other shoulder.
This could make the character look less "pushed" and more balanced (but this is your choice, mine is just a suggestion).
Also, the thing on his right shoulder looks damn cool and interesting, but what is it? Is it a weapon? Or just a piece of armor? If you can, explain it to me.

In the end I also liked the little information task you added. Not too much informations, and the one you added are good enough to make him look interesting. I just don't get why he is a guitarist tho. It's like seeing a future lawyer becoming a farmer... meh!

In the end, this is a great piece of original character!
Nice freaking job.