http://www.brainfreeze.be/2013/03/19/brainfreeze-speelde-injustice-gods-among-us-een-hands-on-preview/

Alternate costumes/skins are mentioned possibly being worked on by NRS. These include Flashpoint, Superman: Godfall, and Batman: Knightfall
When speaking with Hector Sanchez on the topic of bosses, he suggests that at least one boss will be a playable character, but a much stronger, powered up version of that character. No definite number of bosses is mentioned
Huge Strange and Arkham Scarecrow will make cameos
Aquaman's character trait (dripping with water) allows him to somehow "slip" out of combos
Ares shows up in a cut scene (picture included on the website)
Also making cameos: Darkseid, Gorilla Grodd, Martian Manhunter, The Atom, and The Parasite
XP allows purchases for locked modes, art concepts, costumes, etc.
"Classic Mode" is just like single player for MK9. You have to play through a list of opponents and end by winning a boss fight. Winning this mode unlocks ending videos
The Article mentions a survival mode where you have to defeat all opponents on a single life bar
There's apparently two spins for Classic Mode. One is called Time-Attack (not sure how it works) and the other is called Poisoned Mode. Here, your life bar slowly drains
Also, there is a Single Battle mode where you select your opponent for a single fight
Interested in fighting environments? The article says we'll have TWO Asylum's: Arkham Asylum and Joker's Asylum

Dose anyone read Dutch?

Joker's Asylum sounds interesting