Moé stages...
But in all seriousness, costumes, art, silly videos and pictures (bla bla bla cooking with scorpion, been said a billion times for every game since its inception) are what I expect. It's about all I want, really
Characters cause logistical problems competitively, unfortunately, so the less of that the better. Depending on whether or not stage choice becomes a significant factor in this game, that could be an issue too. Best to keep it cosmetic.
That said, I really wish devs could compromise and bring back ye olde cheat codes so that TOs (and players that pretty much only care for multiplayer) could get unlockables straight away while leaving lots of stuff to unlock for those players that enjoy taking their time to unlock things. :\