Many artists work only with paper in their collages. You can buy handmade paper at a premium, which often has fibers, flowers, leaves or other elements woven into the surface. But you can also use all manner of consumer-grade paper, from wrapping paper to vintage postcards, old stamps to magazine pictures. Many collage artists integrate found paper elements into their collages, such as candy wrappers, stickers, packaging and bits of text from newspapers. Collage artists dabbling in mixed media might include beads, shells, wax, bits of jewelry or coins in their compositions. You can also used ripped paper in collages. Note that ripping toward the grain of the paper creates a smoother edge and ripping against it creates a jagged edge where the white paper underneath the dye shows.
Primed mounted canvas is an excellent support for collages, especially those that are so layered or heavy that they may bend paper. Other collage artists use primed canvas panels, slabs of wood, shipping tags, baseball cards (sometimes called Artist Trading Cards or ATCs) or thick paper. Collage also works on furniture, particularly stools, tables, shelves and shadow boxes, but then it is called decoupage.
When working with papers of varying thickness or doing mixed media, it is particularly useful to seal the surface of each collage element to keep it from warping or curling. A common method is to lightly coat one side with matte gel medium and let it dry. It may curl slightly while drawing, but then coating the other side should flatten it. After both sides are dry, you can make the collage element more flat or rigid by placing it between two sheets of wax paper and weighting it overnight. You can do the same thing with a finished collage that is on thin paper. When you are done with a collage, you may want to lightly coat the surface of the entire composition with matte or gloss gel medium.