I am by no means currently capable of rendering an illustration like this, but I would like to address one issue I have with this. I personally don't feel like the head of the character stands out well enough from the background. I've seen your work, and I know you're really good at pushing values where they need to be pushed, I would endeavor to do a little of that just to separate the head from the background.
Otherwise this is an impressive illustration. Keep up the good work!