The good: You've done a far job on his face. I can see shading there, his eyes aren't really well defined, but definately good enough for table top play. Your different colors are mostly in the right places, except for the brush marks on the base. This would be an easy fix to paint over those, and doing that would improve the look of the mini drastically.
The bad: Your white needs shading. If you want the really pure white look, try painting it space wolves gray, then hitting the high spots with white. Or put a thinned out wash of shadow gray carefully in the grooves. That would help draw out the little details. Also, I know the gloss sealer is really good at protecting, but it makes the mini look horrible. For the best of both worlds, put on a coat of gloss sealer, let it dry, and then hit it with a couple of coats of matte sealer. Then you get the protection of gloss, and the look of matte. Hope some of this helps! :)