I've listed them in the order I painted them. Snape isn't quite where I would like to finish him- I'll probably go back and fix him later, but anyway- I think there is an obvious improvement from first to last. I learned it's easier to work with high contrast images, and to use soft brushes for the majority of skin, and hard brushes on fine small details. I also learned that it is much easier to paint using only blank, white, and one midway grey, and mess with their transparencies rather than trying to match every shade.
So yeah, I think I've achieved something here. I'm quite pleased with my progress. : )