It isn't a warhammer movie, but I think it manages to strongly capture the tone of the warhammer setting. I thought I would suggest it to people as a potential mood-setter for their warhammer sessions.
Check out a movie called "The Black Death"...
Couldn't agree more, it would only take a slight change in costume to make it a good Warhammer movie set during a time when Nurgle is most active!
It also has a perfect soundtrack for WFRP gaming IMO. Highly recommended.