The mosaic below is made with ceramic and quarry tiles. Artist got these free from local tile shops (old and broken stock that would be used for landfill). He used an electric wet diamond wheel tile cutter to carve the tiles, mounted it on marine plywood, using a flexible cement and than he grouted it. The size of the Escher piece is approx 2' x 2' and took about 1 week to complete.
The work of David McDonagh would be considered a type of mosaic. He calls his style 'opus sectile'.
Artist's deviantART profile http://davidmcdonagh71.deviantart.com
The image was found at http://davidmcdonagh71.deviantart.com/art/escher-inspired-96179820