I use 3 monitors and been using a aweet program found on Komando.com, Johns Background Switcher from:
www.johnsadventures.com
http://www.komando.com/downloads/category.aspx?id=4996
Lots of options, but no video at this time, but John is going to be taking another look at it.
http://johnsadventures.com/forum/topic.php?id=1136#post-4829
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As for DreamScapes, only my center monitor works in animation and the other 2 show only a still image if the animation 
Bummer!
But, if I take a .wmv and set it as my background, then all 3 monitors will animate the same just fine. Its just dreamscapes that does not support multi-monitors in video loops, for me anyway. 