Okay, I know we're sick to death of hearing about Super Unlockables and all that shit, but here are some things I've noticed that lead me to believe there is A LOT more to discover, whether it be characters or arena or whatever...
Shujinko's Ending: Clearly in the first picture when he's describing his defeat of Onaga and how all the training from the warriors aided him, Jax and Johnny Cage are pictured, along with most of the characters from the select screen.
In the Order Realm: Whenever I talk to to Fujin anymore, he tells me he'll talk to me in Earthrealm, however I've never seen him...
In Outworld: Lui Kang tells me he'll talk to me later...
Kontent: A lot of empty spaces are in most of the categories. There isn't the entire soundtrack, only a select few songs, and songs that I haven't heard anywhere else in the game. Also, there are only a few martial art movies, wouldn't it make sense to have one per style?
Arenas: The Golden Desert Arena has it's own music according to the soundtrack section of Kontent. But whenever I play in the arena, Lui Kang's tomb is what I always here. Is this a result of the arena being out of order, and more need to be discovered to make the music and the arenas match?