Could always do some ice type Pokemon. Those are always a treat.
Or you could have it be a 'whatever the winner wants' too.

i was thinking a pokemon would be fun! ice types.. ill think on it!

Yeah ice types could be fun like Glaceon, Alola Ninetales, or Aurorus.

Adding to the other comment, I definitely think something like ice pokemon or pokemon connected to christmas in some way, like a mega sceptile with its tail or a deer mon could be a lot of fun!

awwww thatd be cute!