Very cool! Actually, the most famous photo ever is...

the one of Che Guevara taken when he was looking up at Fidel Castro when Castro was giving a speech. That photo has since become part of pop-art culture, and has been reproduced many millions of times over the past 50 years on t-shirts and flags and the like. Even now it is easy to go on the internet and find a t-shirt with this photo emblazoned on it.

I believe that the most famous photo when America only is considered is the flag-raising at Iwo Jima.....