@Yop: Indeed. Everyone is suspecting the villain is going to be the Fallen. If you don't know who he is...he's one of the original thirteen transformers created by Primus(God of the Transformers), to combat Unicron(Primus' evil opposition). But, Fallen betrays Primus and sides with Unicron. Fallen and Unicron were defeated by Primus and sucked through a blackhole to be sent to another dimension. Unfortunately for Fallen, he was trapped in "underspace"(between dimensions).
This guy is like the Cthulhu of Transformers.
"The character appears in Transformers: Revenge of the Fallen (2009). Director Michael Bay described him as "apocalyptic". An endoskeletal robot with large tentacles, which is behind the wall painting, was hinted at being the Fallen."
Also, I suspect if he appears in the second film, it will set the third film for the return of Unicron, which will also be epic.
The image is working fine for me. I added the image as an attachment to the first post, so you should be able to see it now, or just go here to see the image:
http://www.comingsoon.net/news/movienews.php?id=51802
Here's an image of Fallen from the comics:
http://www.bamkapow.com/ul/772-Thefallen.jpg