Thanks to great websites like airliners.net and aviation-safety.net, and also many reference books, pictures of almost every individual airliner are now available.
The only 747 of which I don't have any pictures yet is N752PA, a 747-121 of Pan Am, named "Clipper Fortune". Only 5 months after its delivery, it was destroyed by terrorists in Cairo on 6 September 1970.
Given the prestige of the 747 in the early 70s, I'm sure pictures of this one must be dusting away in slide or PR archives... Thanks!