Update: Jacques Distler is live-blogging: MondayThe Reference Frame is the only place in the world where you can learn that the painting is "Blind Man's Buff", 1788. No, it's really not "bluff" as the page indicates.
Because I have learned that not everyone understands the painting, let me tell you that the blindfolded female aristocrat in the middle symbolizes the bulk of M-theory and the similarity with the hexagon drawing is no coincidence. We haven't been told whether the participants will play this M-theoretical game after the talks. :-)