ARTstor has nearly a million images of art, architecture, and design.

Britannica Online has images, diagrams and more. Be sure to narrow your search to multimedia.

CREDO Reference has images and diagrams from numerous reference sources. Click "preferred" for Images in Results.

Oxford Art Online contains over 40,000 images.

The Drake Heritage Collections have historic images of Drake and Des Moines.

The Life Photo Archive hosted by Google contains "millions of photographs from the LIFE photo archive, stretching from the 1750s to today." Particularly useful for historic photos of American life. Searchable.