Well, snow, for one thing.
Christian Bale and Christopher Nolan spill some of the beans to the Pittsburgh press as filming begins:

“Nolan confirmed that they will be simulating snowfall to show Gotham City in winter, that Heinz Field would be used for a football game, and that they would be shooting scenes in Carnegie Mellon University. Bale promised there would be “fighting in the streets, a great deal.”

IO9, via Pittsburgh Business Times.

And Kenneth Branagh is out for the “Thor” sequel. Star Chris Hemsworth shares with Hero Complex:

“I’m really disappointed. Ken built that character, and everything I know about the Thor world, I learned while shoulder-to-shoulder with Ken. I learned so much from him… As long as he’s happy, that’s the thing. I learned so much from Ken while we built [the first film], so at least I had that time with someone like that. The start of anything creative is the most important period in a way. That’s when the most can go wrong, and Ken made sure we got it right.”