Fred Diamond offers a free and simple set of miniatures rules for playing pony wars — US Cavalry vs Indians.
If you’ve wanted to try out some of the outstanding western games that are in print these days, but don’t hvae the figures, you could download and print these sheets of 19th century western gunfighters, animals and other assorted things.
Tim Greene has a good site for playing miniatures wargames set in the victorian American West. There is lots of information on the combatants, plus battle reports and rules reviews.
Fred Diamond has a simple set of free wargames rules for playing the Indian Wars in the America of the late 19th century.
I’m currently painting some of Wargames Foundry’s Plains Indians for a 7th Cavalry game. I found this site, with descriptions of symbols that the Native American warriors painted on their horses.