This is Skyrim's first piece of downloadable content, Dawnguard, which comes out tomorrow for Xbox 360. I loaded it up for the first time about half an hour ago. Headed to the first new area, Fort Dawnguard.
The video above shows what I found there. Enjoy your first look at Skyrim's DLC in action.
(Exiting and re-entering the room seemed to fix this issue.)