You may want to try searching for an image in print. This could give you more information about an image by letting you view it in the context of a book or article. Here are some reference books that may be of use to you--you can look them up in the catalog.
World Painting Index by Patricia Havlice Pate, 1973-2003.
International Guide of Art Experts, Specialists, and Catalogues Raisonnes by D.M. Klinger, 1993 or
Art Books: A Basic Bibliography of Monographs on Artists by Wolfgang M. Freitag, 1997.
Index of Medieval Art.
Oxford Guide to Classical Mythology in the Arts, 1300-1900s by Jane Davidson Reid, 1993.
Dictionary of American portraits by Hayward Cirker, 1967.
Index to Reproductions of American Paintings by Lyn Wall Smith, 1977.
The Visual Resources Collection, located in McCormick Hall, has a collection of over 500,000 slides. The slides can be borrowed from the VRC for presentations and studying. The VRC also has a collection of photographs that can be consulted for research.
The School of Architecture also has a Visual Resources Collection. It contains slides and lantern slides as well as drawings and slides of student work. You can visit them at the Architecture Building to browse the collection.