Often an unusual, seemingly unrelated combination of materials work best.
Here is a list to get your creative juices flowing;
Beads
Cardboard
Clay
Drawings
Edible materials
Found objects
Fabric
Glue
Ice
Jewels
Marbles
Metal
Paintings
Paper
Plastic
Sand
Stone
Wax
Wire
Wood
Here are the cool mixed media creations kids from around the world made in response to this challenge.