Well, we could always fine-tune S.Z.'s engine to allow for some kind of multi-player, or something...I dunno, just saying what comes to mind, I guess.
We could always have a writing contest, or maybe a drawing contest...but that'd alienate some who cant really draw well enough.
How about...a Klonoa impersonation contest? Everyone impersonates Klonoa, and battles to the death.
We could also all just try to speedrun the game, and each of us posts our best times. We'd all be playing the game simultaneously! And since it's so short, we could do one game in a day! That way, those who don't have one game can still participate another day, or something. Maybe...not have it limited like that. Just a one-week thing. That way, those who may be busy one day could still play on another, or something. Heck,, it could even be a charity event, or something along those lines.