Here’s an interesting set of Flickr photos of pre Revolution Moscow.
Here’s a Library of Congress page with scads of stereographic photos from the Civil War.
For Wild West fans, here are a bunch of period photos of the American West.
Fans of pulp and other inter-war gaming might be interested in seeing these rare color photos of life in the US in the 1930s and 1940s. It should give you some good ideas about colors.
Here’s a neat photo album – history of the US Philippine War 1899 – 1902.