Metropolitan Museum of Art
Metropolitan Museum of Art: Louis C. Tiffany
Louis C. Tiffany created fabulous mosaics, stained-glass windows, Favrile glass, lamps, enamels, ceramics, jewelry, metalwork, drawings and paintings. This site provides details on his life and work with wonderful images to explore.
Tech4Learning
Pics4 Learning: Images for Education: Mosaic
Dozens of photos of mosaics from around the world add to this useful reference. Browse through the examples, then click to enlarge.