I love me costume variety, but new stages would also be welcome, and in third place, taunts, intros, and outros.
Variety really helps in any game.
They could probably only get one more costume for each character though, since there are some limiting reagents with characters that don't have many other costumes left. It'd still be possible to have characters with more individual costumes than others, but if they were to only do costumes in whole packs, that'd probably be it.
Alt account of NDgamer1122 Soon to be my main once I have enough Karma >.>