I used to run it on a different gaming forum, and we did topic like: Vehicles, Gaming then split that into subtopics like Shooters, Fantasy, etc. Topics like Animals, Extreme sports, roller coasters (lol), Anime, Space, The Sky.
You can do topics that leave the sig up to the Imagination, like say the topic is "Time", that is really wide open to interpretation.
we have done thos already but still some good one in there
also for weeks we do wanna do a fighter we can pick a fighter from the upcoming ufc event like example the topic could be a ufc 96 fighter and we have a good range of fighter to pick from