The best site I found was actually a collection of materials for a Korean history course at the University of Washington. The images collected there are outstanding, whether they’re of the Silla-period Sokkuram Buddha, Koryo celadon, or Choson paintings. And the photos of the Japanese occupation and the 1980s democracy movement are wrenching.
While reading Korea’s Place in the Sun: A Modern History, by Bruce Cummings, I came to a passage on the glories of Koryo-period celadon and decided to look for some pictures online. I found plenty of information — some in rather curious places.