Some characters have a few more costumes than others naturally (hello Kitana!), but that’s ok. Some of these unlockable costumes can be found in the Krypt, but the majority of them are unlocked by doing specific things with certain characters in various different modes of the game. Mortal Kombat X (aka Mortal Kombat 10) has a nice list of hidden alternate costumes that you can unlock in all console versions of the game.
