Edit: I usually don't post updates so soon after the first.
But I was working on the image again, a few more layers + different blending modes made it much better.
The new one is on the left.
What do you think?
Edit2: Just 1 more. ok I'll stop working on this for now
Sorry people, No Tutorial possible. You just have to study human faces, where the light and shadow should be.
But I can give some hints and pointers Shape3d plugin for the basic shape of the face. Lots of layers (Don't even ask ) Lots of gradients, blurs, distorts. Eyes done using my eye tut. Hair done using my hair tut. (Tut list on my googlepage [link] )