I hate futuristic stuff. I hope it doesn't turn out like the "Cowboys and Aliens" movie which was a complete waste of time to watch.
I hated that movie just as much as you did. Believe me, it's not one of my sources of inspiration. ;)
When you say Space western. Do you only mean like a western sort of, wild/outlaw, society or the classic wild west in specific. Architecture, saloons, hats and everything.
Breaking it down, I would say that it's the environment and the atmosphere of the world. The wild is an uncharted, mysterious place of criminals and bandits. Civilization behaves in a similar manner to how they did.
To elaborate on how the setting is coming together
in my head: Somewhere not so far in the future, an alien world shatters. The occupants survive, but technology has declined to a point preceding that of the 20th century. The game takes place between a chain of floating islands and the much larger continent they drift above. One island boasts the ruins of a city, where horses and hang gliders are the main forms of transportation. For a sense of the architecture, refer to that PM I sent you awhile back. Imagine something like that in ruins, combined with whatever materials they had at hand after the "incident", reflecting a west feel as much as I can. The rest of the world is home to bandits, pirates, mutant space prairie dogs, ETC - scattered between the "lowerworld" and the islands.
I'm still completely open to criticism.