Graffiti! Pone based graffiti. Be it something like above, ponies making uniquely pony graffiti, or whatever!
You’ve got 45 minutes to create followed by 15 minutes to submit! Have fun~
By the way, man, this dude Shinoda has done a looooot of MLP wall art. Props. Going as far back as 2012 at least. Seems they’re also the one behind Apogee.