I did some tests with AVI files used as displacement maps. It can give some nice effects. Of course it can take a lot of time since you have to first create the animation for the disp map, and then render the final animation using it to see the results (though you can render a few frames to get the idea first). It would be a good way to make throbbing veins in somebody's forhead, or that sci-fi effect of a creature crawling under the skin.