Pretty much anything.
We have made floating shelves out of Plexiglas, solid concrete, marble & granite (solid or hollow), solid wood (any kind), plywood covered caucus, copper , checkered steel sheets, flowerpots (with a waterproof insert), laminate, corean, engineered stone, arborite (sturdy laminate used for kitchen counter tops), Formica Wilsonart or even just laminated 2 pieces of plywood attached together.
We have used the steel bracket for floating vanities, makeup tables and more. Your imagination is the limit!
Check out this short video on some alternate shelf styles below:
Caucus:
Some customers prefer to use this method, since they want to use different laminates on the shelf.
You build a caucus out of 1 1/2 inch wood (the same thickness as the female bracket), leave enough space to accommodate the female bracket, clad it with 3/16 plywood and laminate that, or choose the plywood you want to achieve the look they want.
You can then cover the plywood with plywood, leather, felt or anything else your heart desires.