This depiction of a charioteer is a Roman-era mosaic from the 3rd or 4th century. The snapshot is from Sebastiá Giralt's flickr photostream.
If you like ancient mosaics, I've just discovered a wonderful blog called the Mosaic Art Source Blog! The post on horses in mosaics is not to be missed! They have collected a wonderful set of photos of both modern and ancient mosaics from a variety of sources, all featuring horses.
Browse the blog for posts on other subjects, too. I loved this post featuring lions.