I'm not completely sure what's happening but I have an idea.
In an upcoming episode, 2x20 i think, Chuck and Vanessa are going to team up to try and break up Nate and Blair. This plan will probably involve them pretending to be dating which would explain the pictures. This is what I've gathered from spoilers and other stuff. Hope that helped!
Ok, I think I've got a pretty good idea of what is going on. I think Chuck is just realizing how much he is in love with Blair. But as we know Blair is going to get back together with Nate, which will not please Chuck. So Chuck figures since Nate stole Blair from him, he'll date Vanessa in order to make Blair extremly jealous. Which Chuck thinks will work, but I don't know if it will.
I really don't know if they would do this, but i think that they may just be trying to screw with us. The pictures with chuck and vanessa could just be of ed and jess. They could easily be behind the scenes pictures...but if not, then I really think that they are plotting agains nate and blair. I highly doubt that they actually hook up.
