There were at least two scenes where the survivors were using makeshift (and real) pistol silencers, and there were a lot of shots of the prison environment. In this Comic-Con trailer (below), there was also some shots of alive soldiers, which is a 1st for the series. There's also a preview of a new area called "Woodberry", which looks like a secure, preserved (or rebuilt) small town that is free of infection. Lastly, that asshole Meryll (sp?) is back, fuck.
I hope I have the fucking time to watch all of S02 this week, like I watched S01 a second time before S02 premiered.
If you plan to talk about anything that would spoil the plot for people who haven't watched yet, put it in spoiler tags!