Paint your windows with your store hours. I've also seen it done with a chalk board propped up in the front display window. Way cooler than a tacky neon "OPEN" sign or those generic plastic store hours signs.
A clean slate. More on painting your shop display windows.
I gave an Autumnal, slightly gothic subtle twist to my window display at The Mill in time for Halloween. I have been finding original Wardian cases and animal skulls to add to the display as well as the tall vases with carnivorous plants.
If you are a retail business with great display windows, take advantage! Decorate for seasons, holidays, organizations, or special causes like shopping locally! (Reform School shop window by Jessica Pezalla of Bramble Workshop)