We had a very small bathroom that we wanted to make very interesting. It had vinyl flooring that was stained and ugly anyhow. When we tore up the vinyl (hoping that there'd be nice tile underneath) we found the original tile in very bad condition. We leveled it out with some quick dry concrete and painted it a dark grey, glued a bunch of pennies down, sealed it, and Voila! an awesome (and very cheap) penny tiled floor.