American Memory consists of over 70 digitized Library of Congress collections of both visual and textual material. The Collection Finder lets you browse by topic, format, time, place, or library division. National Geographic Map Machine includes physical and political maps, satellite imagery, links to other map resources, and the Xpeditions Atlas with nearly 600 printable maps. The Amazing Picture Machine allows keyword searches on an image database which is strong in the areas of art, architecture, nature, famous people of the 20th century, aviation, World War II, the Civil War, astronomy, maps, national parks and monuments, and US cities.
Pictures includes categories for animals, clipart, people, places, space, sports, and more.
If you need a picture illustrating a particular concept, it is often possible to use the online catalog to find a relevant book with photos or illustrations. Search the catalog by keyword or subject. You will notice that the screen which gives you a book's call number also tells you if it has maps, illustrations, portraits, etc. Abbeville Press, c1991. O'Keeffe, Georgia, 1887-1986.