The Google Art Project: Like Street View for Museums
http://www.googleartproject.com/ gathers together seminal works from Germany, Russia, New York, and 14 other locations online. The interactive street-view-style interface makes even hairline cracks visible. New York's Metropolitan Museum of Art and the Museum of Modern Art are among the participating galleries.
Dutch Paintings of the Seventeenth Century
This is a Getty initiative and is a digital catalogue produced by the national gallery of Art, Washington.
Includes stock photography, editorial photos, and some moving images.
A free public collection of photographs from major photography archives. Contributors include the Library of Congress, the Smithsonian Institution, and more.
The Oxford dictionary of saints. Daf REF BR 1710 F34 1997
Signs & symbols in Christian art. (Ferguson) Arch/FA REF 7830 F37 1961
Iconography of Christian Art, 2 vols. (Schiller) Arch/FA REF N 7830 S3513
Catholic Eycyclopedia http://www.newadvent.org/
GENERAL SUBJECT DICTIONARIES
Dictionary of Subjects and Symbols in Art Arch/FA REF N7560 H34 1979b
Encyclopedia of Comparative Iconography: Themes Depicted in Works of Art Arch/FA REF N7560 E53 1998
Hall's Illustrated dictionary of Symbols in Eastern and Western Art Arch/FA REF N7740 H35 1994
Image as insight: visual understanding in Western Christianity and secular culture. St. P BV 150 M47 1985
Dictionary of symbolism: cultural icons and the meanings behind them. Arch/FA REF AZ 108 B5313 1994