Races

Nantuko -- skittery settlers
Rhox -- tough settlers
Viashino -- raiders

Classes

Sheriffs -- Soldiers
Marshals -- Knights
Judges -- Advisors
Bandits -- Rogues
Gunfighters -- Warriors (Rogues? Soldiers?)
Ranchers -- Herders? (Rogues?)
Preacher -- Cleric
Prospector -- Scout
Dowser -- Druid/Shaman/Scout

Flying

Flying creatures are usually mounted on griffins.

Creatures

Sandwurms -- Wurms.
Steers -- Aurochs
Other desert creatures -- as normal