“John C. H. Grabill sent one hundred and eighty eight photographs to the Library of Congress between the years 1887 and 1892. This collection is considered the premier collection of western frontier photography in the United States today. Known for their gritty realism, these sepia-toned windows to the past capture the American West in the midst of settlement. The well-crafted images evoke a definite sense of place and time that allow the viewer to peer into a world that otherwise survives only in our imaginations, and the stuff of legends.”

-Margaret McGuire, 2004. From Digital Picture Printing & Framing

Grabill’s photographs are gritty, realistic, and immediate. The entire collection can be found at the Library of Congress. Several sizes are available for download, including hi-res Tiffs.
I used one of his shots of Deadwood, Dakota Terr. to make my banner and another shot of his is my current wallpaper.
Here’s a few of my favorites:

There are many more her and they are wonderful inspiration for your Western game.