I think grabbing some photo hair and using it for the edges in the hair in the colour map would help quite a bit. Either that or following one of those photoshop texture hair tutorials that are on the net (would post a link but I'm at my brothers)

If you cover the top half of the head with your hand (eyes to the top of the head) then the bottom half of the face looks cool - maybe slightly darker contrasting shadows are needed. Also the shadow on the neck looks quite plastic. The top half still needs some work on the eyes and the hair. It is going great though and is looking damn cool

Showed it my brother and asked who was and he said it was bjork straight away