Digital images taken years ago can add some rich detail to your family history. It can help provide your family with some ideas about what people wore, how places have changed, and how life was different in an earlier era.
The pictures don't need to be of only your family members or pictures that family members have. You could use online archives to find pictures that will enhance your family history.
Here are some of my favorites:
Frasher Foto Collection at http://content.ci.pomona.ca.us/cdm4/about_frasher.php. This collection is located at the Pomona, California library. Burton Frasher was the West's most prolific photographer. His pictures were used for postcards in the early-mid 1900's. He took photographs of locations throughout California, Arizona, Colorado, New Mexico, Utah, and Nevada as well as other states. I used one of his photos taken in the Owens Valley for my book.
The above link includes a search that you can use to look for photos of a region or a landmark.
These photos are owned by the Frasher family so if you decide to use on in a publication, you must get written permission first. The library has information about obtaining permission. Once permission is granted you can obtain a digital copy from the library for your publication.
The USC Digital Archives, http://digarc.usc.edu/search/controller/index.htm, includes all kinds of images including photos from different time periods, places, buildings and people. Collections include images from AAA, the Chinese Historical Society, Mission Photography, Korean American and Japanese Relocation. Use the search engine to type in an address, name, locality, or subject. A search on the term "cemetery" brought up 410 pictures including one of a cemetery in Madagascar, local Los Angeles cemeteries, and Native America cemeteries. Each picture includes a description of the image, the owner and information about obtaining the image.
The Library of Congress Prints & Photographs Room, http://www.loc.gov/rr/print/catalog.html, is another place where you aren't necessarily going to find a picture of your great-grandfather or his house but you will find pictures of places, things, and famous people of different eras. Like the databases above, a search engine provides you a place to search by locality, name or subject. Once you conduct your search and click on an image you are interested in, you will be provided with information about that image. In some cases, these photographs may be copyright free, so that you can save it directly to your computer and use it in your family history.
This is a great site to use if you want a picture of some celebrity that you ancestor knew or rubbed elbows with. It also has some great photos from various eras. You can also search by the name of the photographer, such as in instances when you want to see works by a famous photographer like Ansel Adams.