I want my Western Town to look like someone lives there. A western town's Front Street (a.k.a. The Row) was no different than Main Street, or "The Strip" is today in a town like Ruidoso, Laramie, or Durango. Advertising is and was rampant, and the thing missing from my town until recently has been the commercial clutter that is the inevitable result of economic activity. In short, I have begun to "monetize" my buildings.
Of course you must have a sign on any commercial buildings. Most lettering in those towns was simple, but examples of fancy brushwork can be found easily enough. Time-Life books and internet image searches should give you plenty of examples to paint your own signs from. If you don't have a steady hand, make your own signs in Photoshop and print them on cardstock.
Smaller signs were everywhere on commercial buildings in the Old West. It seems that everyone sold cigars or tobacco and advertised the fact. Saloons might have signs proclaiming their Faro (card game), Billiards, Whiskey, or Dancing.
My latest addition to the mining town of Knuckleduster is poster art. Large posters were "pasted" up by circus or theater promoters in advance of a show.
Wanted posters certainly deserve a prominent place. It takes a bit of inestinal fortitude to permanently glue a piece of paper to the side of a model you just spent a week building, but the results are worth it and besides, life now or in the Old West is not tidy.