We also made these wacky "crammed tiles" during Wacky ART Camp week!
Each artist selected all sorts of unusual objects from our bins of "stuff" and glued as many of them as they could to a six inch piece of sanded board. Then they painted them so as to obscure the original 'identity' of each object while creating an unusual piece of art.
They started by sanding all of the edges of their wooden tiles to eliminate any chances of splinters. Items were then arranged on the tiles first, some very carefully and in a very organized fashion, and others just globbed on randomly to fill up the spaces (which is sort of what I was going for). We used white all-purpose glue which would dry overnight.
The next day we painted the entire tile and all of its objects with white gesso (like white primer, which would also work). This took away any feelings of dread about painting an object the 'wrong' colors and created a nice clean white 'canvas' of relief sculptured tile.
After the gesso dried, the kids painted their tiles using just one or two colors of acrylic craft paint (one chose three colors plus white).
This is a great way to recycle/re-purpose old keys, beads, broken toys and other random little "stuff."