Indianapolis Art Museum, 2013. Photo: Laura Gricius-West
There are a variety of places that you can choose to download pictures. Online image gateways are often the easiest, though you can also choose some search engines to help you find the perfect image that you are seeking.
The following list is compiled from responses to a request for names of websites that offer free digital images to be used for educational (non-commercial) purposes. **Read the fine print to make sure the image is indeed “free” ... the fine print on museum sites often state that there are qualifications. Even Creative Commons licenses depend on the uploader having copyright ownership.
The U.S. National Archives on Flickr
The U.S. National Archives was established in 1934 by President Franklin Roosevelt, but its major holdings date back to 1775. The National Archives keeps only those Federal records that are judged to have continuing value -- about 2 to 5 percent of those generated in any given year. By now, they add up to a formidable number, diverse in form as well as in content. In addition to the photographs and graphic images described above, there are approximately 9 billion pages of textual records; 7.2 million maps, charts, and architectural drawings; billions of machine-readable data sets; and more than 365,000 reels of film and 110,000 videotapes. All of these materials are preserved because they are important to the workings of Government, have long-term research worth, or provide information of value to citizens. These photographs, most taken by agents of Federal agencies over the years, cover a wide range of subjects and themes documented in the work of the United States government. Higher resolution versions of many of these images can be obtained from the U.S. National Archives by following the links located below each image.
OAIster
OAIster is a catalog of digital archival resources that are housed at cultural and higher education institutions throughout the United States. OAIster works in a similar fashion to a library catalog. To limit your search to images, enter in your keyword(s) and select "image" from the list of resource type limiters.