I uploaded a flv. video but the preview thum shows a generic film drawing. How can I change the thumb to represent the actual video image or just put a title in it?

Please see the troubleshooting.

I really didn`t see anything that refers to how to change a thumbnail... got a link?

You really did not find this yourself?
http://www.zenphoto.org/2009/03/troubleshooting-zenphoto/#19