The Artchive 

The Art Museum Image Consortium 

CalPhotos (U of California at Berkeley)

The Clearinghouse of Image Databases (University of Arizona)

COMPASS (The British Musuem)

Connecticut State Library Digital Collections

Digital Collections at Harvard University

Digital Collections in Colorado

Digital Image Catalog (Berkeley Digital Library)

Eternal Egypt

The Fine Arts Museums of San Francisco 

Florence Griswold Museum (Lyme, CT)

The Frick Collection 

Immigration to the United States, 1789-1930 (Harvard University) 

Kentuckiana Digital Library (search all)

Kentuckiana Digital Library Images (50,000)

The Louvre 

Metropolitan Museum of Art Collections 

Fundacio Joan Miro

Picasso (Online Picasso Project)

Museu Picasso

Museum of Modern Art - Collections 

National Museum of African American History and Culture (Smithsonian)

New York Heritage Digital Collections

New York Public Library - Small Town America 

New York Public Library - Images of African Americans from the 19th Century 

Norman B. Leventhal Map Center (Boston Public Library)

Photomuse

Open Access Journals

Scholars Resource (images for teaching art history) 

The September 11 Digital Archive

Smithsonian Images (Smithsonian Institution)

The State Hermitage Museum 

Teaching and Learning Resources (Federal Resources for Educational Excellence)

Wadsworth Atheneum Collection Highlights 

Web Museum - Paris 

Women Working, 1870 - 1930 (Harvard College)

World Digital Library

World Digital Library and Video Intro

Yale Art Gallery - Collections