You say that you are having troubles shading the face. Here's what I'd do:
First mentally separate the face into 4 spherical shapes (the back part of the head, the cheeks, and the nose), and then add the highlights where the light hit's each (remember to keep it consistant with the rest of the piece), then thrown in the shade color, similar to what you've done with the hair.
Maybe that will help you...
Also, just something that sticks out a bit: I know they aren't your lines, but I think the staff may bend too much. Otherwise a great piece so far. Good luck!
