I've always loved looking through stacks of old postcards at antique malls, but it's easy to end up with a stack at home and nothing to do with them. If you keep an eye out for postcards with the same subject, like buildings or beaches, you can frame them together and make some nice and easy wall art.
vintage postcards (look for them at antique malls or flea markets)
frame (I chose a cheap, simple clip frame)
masking or washi tape
paper for your background
First you'll need to make the background to put your postcards on. I pieced sheets of old graph paper together because it looked nice with the blues in my postcards. You can also just turn over the paper that comes in the frame if you want plain white.
Line up all your postcards, then tape them down. Using masking or washi tape is good because it's easy to remove from the postcards if you ever want to use them for something else.