It looks like tile...stone, maybe?

i wonder if you couldn't use plywood with different stains. it's basically three or four shades. Lay out a design on graph paper. Stain 4x8 sheets of plywood. Cut sizes you need.
Could also do something similar with tongue & groove flooring.

I believe it's Tile from the Italian tile line, Rex and the series is called Horn : http://www.rex-cerart.it/en/prods-155-1.asp
I hope that helps!