Pool Party Thresh
Thresh could get a pool party skin for sure! He'd have a lifesaver as his lantern, tiny little tidal waves for his Flay, The Box could be a little kiddie pool, and he could collect little rubber duckies as the souls. I don't know about an outfit quite so much. Maybe he could be a shaped swirling vortex of water; kind of like the water that is the Blitzball playing field from FF 10 cinematics.
I haven't thought that far into the idea but someone from another put this up said I should post this and make it more official with its own post, so here it is!