It looks very nice, you could colour it any way you imagine, you are good in colours, but if you asked for Xod's suggestion I would say colour a lot of blood and gore! >:D
|XOD|

It's looking good so far, may be you should put a bit of cream, purple and white tones on the eyeball to make it look like it's popping out, and I suggest contrasting the background with his face, so he stands out more.