Mod Podge papers to the front of back of them.
Collage on top of bottom of them.
Layer smaller Podgeable on top of a larger one.
Paint them with metallic, pearl or acrylic paints.
Add chalkboard paint to them...3 coats.
Use chunky or fine glitter on them.
Use glitter paints and washes.
Add texture with embossing powder.
Glue gems and decoden items to them.
Drizzle with alcohol inks for a marble look.
Drill around the edge and lace.
Drill and add jumprings for jewelry making.