There have been some images leaked for Batman: Arkham City. Although there is no confirmation that they're legit. If they are in fact not legit, these leaked screens would be the greatest not real/hoax pictures for a game that I've ever seen. The images include screenshots of Batman (of course :p) as well as Harvy Dent/Two-face, Catwoman, a re-imagined Harley Quinn, and your typical Joker thugs. Click the article link below to see the screenshots.
Sorry for double post and necro, but relevant to topic. A new gameplay trailer for Arkham City was released last month and the release date for the game is October 18 of this year.
The trailer looks good but nothing too spectacular imo, although Batman grabbing on to the helicopter is pretty cool.
I also read somewhere that 80% of the game will take place outdoors in the city and that the game will not be as linear as the last one meaning you can explore more and complete tasks out of order.
Also this (below) is an older teaser trailer but still good nonetheless, and as you can see from this teaser trailer Hugo Strange will play apart in the game :)