I love old postcards. Whenever I go to an antique show, I can spend so much time at the booths that have postcards, just thumbing through them.
I haven't come across any movie-related postcards, but I mostly collect pre-1930s cards, so they probably didn't make a lot of movie-related stuff for the public back then.
I collect old European towns (pre-WWII, before they all got bombed out).
And real photo postcards (RPPCs), which were developed from the negatives directly onto the card face. They are often one-of-a-kind scenes showing fashion and social history. They are also often hand-tinted, which lends a vibrant - if characteristic - vintage look to the images.