Sorry, but Imagevue can’t create thumbnails for video because your server doesn’t have the modules to do this. Instead, you can create thumbnails manually if you dont want to use the generic thumbnail video icon that is automatically created.
viewtopic.php?f=26&t=4243&start=0
You would need to take screenshots of your videos or use get thumbnails somehow from an app on your local computer. I found these applications which might be handy, although I didnt try them personally:
http://sourceforge.net/projects/thumbnailme/
http://sourceforge.net/projects/moviethumbnail/