Oxford Art Online is an art reference library that searches Grove Art Online, The Oxford Companion to Western Art, The Concise Oxford Dictionary of Art Terms, and The Encyclopedia of Aesthetics. This resource contains images, biographies, subject entries, and thematic timelines (antiquity to present).
Extremely rich site for understanding the art of a particular region and time. Use the Time Period and Geographic menus to see key Works of Art, Related Exhibitions, and, under Related Content, Thematic Essays.
ArtStor presents a rich collection of digital images drawn from colleges, universities and museums. At the top of the page, click on "Enter Artstor Digital Library" and either login or sign up at the top of the page. By registering on the site you can make personal image group folders and download images.
Use the Advanced Search to specify geographic areas, time periods, subjects and artistic media.