Sites that feature information on a country, city, or region frequently include maps. All images produced by the federal, state, and local governments are in the public domain. That includes NASA images. The consumer systems are among the best places to find public domain images. Members contribute their own work, often in the spirit of sharing rather than to make money.
Clip art is often in the public domain.
Do not assume that images are in the public domain if they lack copyright information. Many people are unaware of their responsibilities with respect to copyright and publish images illegally. For more information, refer to Chapter Twenty-one. NASA is a major source of such pictures, but observatories and space-related institutions around the world contribute too. You need special viewing software to look at these pictures.