Creating unique window graphics and other signs for your storefront is a good way to avoid copying other brands, even accidentally, and it also will help smaller companies maintain a strong identity against larger competition.
Consumers should be able to easily distinguish between your company and its competitors at a glance by recalling the specific attention to details that make your logo really stand out. PennLive recently reported on an infringement case between 7-Eleven, the nationally recognized convenience store chain, and a local business in New Salem.
This smaller outfit, called Super-7 Food Mart, was found to have a logo far too similar to that of 7-11, especially considering they work in a similar business. Both logos feature a "prominent Arabic numeral 7" as well as the colors green and white, with a word intersecting the body of the number in the center. The name itself is similar, but it's the way this image is designed that specifically found Super-7 Food Mart forced to destroy its previous signage, merchandise and other brand identifiers.
Not every case of a logo infringement ends with a call for overturning a design. A photographer has contested that his image was co-opted by Nike for the design of their "Jumpman" logo, which the court said isn't justified, because the contending photographer's work isn't "original."
If your business has hit upon a truly original element that will help it stand out, it should emphasize this in every way possible, from POP signs to other custom images made for different surfaces in and around a building's brick and mortar location.