You can use drawings, phrases, photos, whatever. Just keep in mind that the thinner the item, the better it will work. For thicker paper like playing cards, make sure you're gluing them to a totally flat surface, so that your paper won't pull up at the corners. But whatever works for you. Needless to say, this is a great hobby for magazine hoarders like myself.
Tabloids are also great source of inspiration.
If you don't want to cut up your favorite magazines, or if they happen to be collector's items, like the vintage confessions magazines I collect, color copies are the way to go. They're only a buck each at your standard copy shop. Scissors or a razor blade Cut out your images on something that you don't want to scratch. Glue You can use regular Elmer's glue, which dries clear or acrylic gel medium from a crafts store, which is more expensive. Famous and accomplished decoupage artists swear by Mod Podge, because it comes in a cool jar.