Some back design feedback:
If you're going to use the first design, scrap the money bags, or at the very least remove the $ signs. It looks kinda cheesy with them. Maybe you could replace them with more floral designs or possibly Sheriff Badges?
I think the second back looks better in the state that they're in. But if you use the 2nd back, be sure to either remove the blank ribbons or make them more intricate. They look like a text banner that just hasn't had the text put in.
Now, you could put words in them, but I don't see what you would have them say. Wild west quotes would look cheesy, and the name of the deck would look distasteful, IMO. Plus, if a back design has text, it's usually in Latin. ( The T11 Sentinels deck is one exception, but it has Greek lettering. The Majestic deck's back has English, but I think it looks pretentious.). Latin wouldn't fit the design, not to mention the deck works OK without text. Maybe swap the ribbon banners for a more interesting scroll, or an object? I think a rifle or a length of rope would fit the design perfectly. The rifle would probably work better.
I also think you should do something about the skulls on both the back designs. The skulls look out of place, and makes it look like you took the idea from the Calavera deck.
http://www.kickstarter.com/projects/1894542039/calaveras-day-of-the-dead-inspired-bicycle-playing?ref=liveYou could make the design more unique and cohesive if you changed them to cow skulls.
Also, that's a sweet gaff!