There is a post to which you can comment with your own challenges - but please check the masterlist first so that you don't duplicate any already requested. Read the rules, because there are certain limitations on what you can request. ;)
There are only four posts so far at the comm, so I'm not linking to the masterlist and the challenge request list - you can find them yourselves.
Go, read, challenge, and consider what gauntlet(s) you might want to pick up. ;)
ETA: It's a multi-fandom comm, so if, for some strange reason, you wish to request something Non-Spander (though I'm sure that never crossed your minds...) you can. But I'm sure you wont. ;)