I think if the 10th's daily pic has anything to do with a Kirby game, MYYY guess is that it will be a new stage!!
There hasn't been any Kirby related stages shown yet, and I'm sure there's a good amount of stuff to choose from. A stage inspired by Triple Deluxe sounds like the obvious choice, but I'd love it if there was a stage from the Kirby games from back in the day- I always thought of the room right before you fight Dedede in Kirby's first game-
(Like this, with the two basic platforms, and occasionally hazards could come flying out from each of the doors)
Or an awesome boxing ring like this-
(Oh wait, this one already happened-- DEDEDE CONFIRMED!!!1!! ;D )