You can't have an actual VIDEO as a signature but you can make one out of a video. Just open up the video in vurtualdub/ mod and then 'save image sequence' all you gotta do now is open up your preferred animator program e.g. Image Ready and insert the whole image sequence and save as an animated GIF. Voila. edit-- Here's a guide for .mov files to .gif http://www.riverpast.com/en/support/tutorials/convert/mov/gif.php
