Arkyves provides access to more than 500,000 images and textual entries from libraries and museums in many countries, among them the Rijksmuseum in Amsterdam, the Netherlands Institute for Art History (RKD) and the Herzog August Bibliothek in Wolfenbttel. More collections will follow in the near future.
From the Brill website
Artnet is particularly useful for its high-resolution images of artwork sold at auction and not necessarily held in public collections.
Fine art sold at auction, 1990s-present. Most records include descriptions and color images. Auction results with images for individual lots sold at major houses since 1990. Database includes paintings, sculpture, and works on paper. Records are searchable by either artist's name or auction house.
Largest and most comprehensive collection of high- resolution images on topics across the humanities, social sciences and sciences.
Image database covering architecture, painting, sculpture, photography, decorative arts, and design as well as many other forms of visual culture. Select "Search and Browse for Images" to begin using the database.
Records works of art (manuscripts, metalwork, sculpture, painting, glass, etc.) from early apostolic times to A.D. 1400 with emphasis on art of the western world. Includes bibliography, references to reproductions, and some links to images. Apostolic times - A.D. 1400. (Formerly Index of Christian art.