I just read a thread about how to have butterflies fly across screen,(I can't find the thread) but, here is a quick example, which have unlimited possibilties. Its an animated gif over a photo.

http://www.hughmobley.com/Untitled-1.html

That just looks like the little animated butterflie you get in motion with final cut studio. You have to put motion paths and keyframes on it etc

Andy.