I love lego. I have a whole room full of it
Unfortunatley I don't have the mindstorms. When I was a kid, I wasn't into programming, so I was never interested in the mindstorms. Didn't know you could program it with java though. It's sound like loads of fun. Anyways, as for ideas, perhpas you should just come up with a little lego city, and see if you can muild a monster to wreck it