Biggest EVER turn on? Easy. Alfred Cheney Johnston's photographs of the Ziegfeld girls. WOW! I don't care that there's a hint of nudity but I just go nuts when I see his photos. I'm totally amazed by them.
Regular likes :
Historical photos, either of people or landscapes, preferably from around the Civil War through the 1940s.
Landscapes (b/w) or sepia
Action photography, especially football, ice skating, hockey...I love sports photography - color or b/w