bubonicbryan designed an animated lockscreen with clownfish swimming around. The only way i can think of is to possibly replace the images you have chosen with the original clownfish images and then activating in winterboard hope this helps!
hmmmm, I'll have to give this one a try. I tried this other rotating lockscreen wallpaper app, but it would disable my battery theme while it was charging
EDIT:
nope, its just a simple background with clown fish going across it... not so much a rotating wallpaper