I think Clayface would make a interesting villain to join Injustice. He can shape shift to anything and it would be nice to see if he makes it in injustice. Killer Croc would be another baraka type character. What do you think?
Croc is cool but nothing special in terms of gameplay design potential: just another big brawler type, really.
Clayface on the other hand has all the potential for unique gameplay design and animations. I've been arguing for his and Swamp Thing's inclusion since I:GAU for that very reason and something tells me I'm going to have to settle for winning half the battle.