It seems like a handful of specific AA photos (Half Dome, the Glacier Bay leaf) are well enough known to be fairly iconic.

I found a few more by googling "famous photographs": the green-eyed Afghan woman, the "Surgeon's Photograph" of the Loch Ness Monster, Buzz Aldrin on the moon, JFK Jr. saluting his father's coffin, the cover of _London Calling_, the guy in front of the tanks in Tiananmen Square. I don't know if Marilyn Monroe's skirt counts; it didn't start as a still photograph but is a whole lot more famous by itself than the surrounding movie is. None of those are "art" photos per se, though, except maybe the album cover.

-NT