If you're still looking for challenge ideas... I've been playing a lot of X-com lately...
Crips vs. Bloods.
Each side has a team of 6 rookie X-COM solders. Conventional weapons and body armor only, but each solder can choose any item from the game. Some items are useless though. Silly names encouraged.
Dunno how it'd translate for a video, but I've been trying to get a recording myself of that particular challenge. ;3
Another challenge idea for you, Requires Faster than Light.
Faster than Stars.
This is a time based challenge, and it's probably subject to the RNG being mean. Players can choose any ship from the game, and the first player to reach a predetermined sector (3 or 5) wins. Pause is ill advised, as this is a real time race.