You need to check the copyright restrictions on the visual texts available here, but the New York Public Library has a searchable online database of a wide range of historic photographs, posters, maps, and book pages.

This is a tremendous resource for historic visual artifacts in U.S. history. The database of photographs, posters, cartoons, maps, billboards, and so on is searchable in several different ways, and many of the items are available in high-resolution.

This well-designed website is a collection of maps, paintings, architecture, and photography. You need to check the rights restrictions before using any of the resources here, but there is a wide and deep range to view.