Now I just have to finish writing it :P.
For those who are interested I used the most fabulous tutorial to help do the faces:
http://youtu.be/CUbMmzk2_Lo
This woman has the most helpful tips about using Photoshop that I have found yet. It seems the secret is the smudge brush :D. Took me about five hours to complete the faces and then another couple to decide how to put the cover together.