One of the best WW2 picture galleries on the net is at Mission 4 Today, ideal for WW2 flight sim livery makers because the detail is so fine on many of the pics that you can count individual rivets..-

http://www.mission4today.com/index.php?name=ForumsPro&file=viewforum&f=92

Example: Devastator on Pacific carrier manoeuvres, prewar 1941

Absolutely incredible.  I just looked through the whole set.  Just stunning photos that make it seem you're right there on the scenes.

One photo of personal interest was the P-51 parked at the old University of Miami location with students sitting on the fuselage and one of the wings.  The cars in the background date the photo at about early 40's.  You can clearly see one of the old campus classroom buildings in the background.  That classroom building still stands today in Coral Gables, Florida, having been converted into apartments or condos several decades ago, well after the UM relocated to its present site.