We're not sure what's going on here, but Serena sure looks good, whatever it is! The photo is taken from "Limitation of Life" from Season Three of Gossip Girl.
Olivia: I was just thinking, I didn't really give you a chance to know both sides of me. And I guess I was wondering if you'd still want to. Dan: [pauses] I don't know why I'm pretending to think about it. Yes, of course.