Maybe you're searching for a more specific artist. If you're into Ansel Adams view a new computerized exhibition of his photographs. If you'd like to browse on the subject of photos in general, you'll enjoy this directory. It houses many different photographs by yet unsung photographers. This link allows you to wander through the many rooms of the Louvre and view works of art from all through the ages.
Exhibits change from time to time to include featured works of art.
Another online museum you can visit like the Louvre is the Krannert Art Museum at the University of Illinois, which is slightly less known but also full of rooms you can wander through. The gallery includes both paintings and sculpture. To browse in an interesting list of pictures by these specific artists, contact Nicosia in Japan. Here we've found a Rene Magritte exhibition, several paintings by Gustav Klimt, and other paintings which might be of interest to you. If you're into computer graphics, check out a couple of fractal data bases.