You could mix chicken wire and foam. Bust up a bunch of foam scraps, and start gluing them randomly to the chicken wire. Then use a few cans of Great Stuff to fill things in. Once it's all dried, use acetone in a squirt bottle, and a heat gun or propane torch, to deform and distress it. After your texturing starts to work for you, a couple coats of paint will be easy to add. The foam should be quite rigid and durable, and kids touching it won't wear it out as easily as aluminum foil.