I'm not the greatest for CC, but here are some things that, if remedied, may improve the piece.
His hair looks a bit more like a tightfitting helmet than a 'doo, so why don't you break up the monotony there and add locks, and try not to use a generic pillowshade effect there. Infact, I see an overall pillowshaded effect, partly because it's mirrored. Very few are the times that a mirror-job is going to work, try to go through the entire piece pixel by pixel, eh? Also, you should extend the mouth a couple of pixels on either side. Add eyes...
...and, err, I'll leave the rest to someone else, I'm not feeling it tonight.