Gandalf the Black!

I meant to finish off my Dahomey Legionnaires today but fell asleep in from of the TV(!) so a complete lack of progress hobby wise. However I did come across this wonderful picture by Benjamin Collison, and it got me thinking...

I was wondering about alt-historying The Lord of the Rings, maybe having Gandlaf the Black with Gondor in his thrall up against the free peoples? Possibly a three way bad guy fight between Gandalf, Sauraman and Sauron? What if Frodo had kept and used the ring? Could be fun and all you'd need to do is paint a Gandalf black.