I stil think the Florentine shadow is probably someone behind the frame lit by another flash, but it sure freaked the security guards that I showed it to out !
What is this frame you speak of? I don't get what you're saying, but I don't know the place very well.
The only thing I can think of that could have done this would be a prank by the guards. If there was a spotlight at the other end of the room the light could be diffused with something and a cutout would be put in front of it to project to the wall. That's what it looks like, a cutout! But, since there are other pictures of the same area with no shadow, and no one could have come in from the back and put it up there momentarily (that I'm aware of, at least), and a photo taken from that far away of any shadow would never produce such a crisp outline, or such densely black color, I am going to end this very long sentence by challenging Adam to a duel! I think this is the real deal Sir!