I'll promote Motion again, as it is a new topic for Caedes contests. It can be represented in numerous ways by photographer and computer abstract artist alike.
I do agree that motion, as a theme, can be fun. But time and time again, photo-centric themes are chosen for the contests. If not for this current contest, perhaps for the next, why not step out of the sandbox and let some of the other kids play for a while?
I suggested electricity. I thought it'd be something everyone can work with. Electricity can be seen, as in lightning, or something that is felt. I think it could also be represented in many ways, such as shapes, colors, patterns, etc. Just need a little imagination. =)
If you've ever wanted to make a difference but found it hard to believe that one person could... check out the Kiva Team Caedes discussion thread and discover that anything is possible.