I'm sure the Deathfields audience will have delighted in picking up some Terror Birds from some point in history and turned them into a cavalry mount for some poor unfortunate fighting force....
Cossaks 17th/18th century ?
Maoris shortly after contact with the west so they've got guns etc, but also all of their tribal identity?
Arab (not sure about this maybe keep them for the space camels your sure to have in the works)?
American Indian? (Comanche)