I know what you mean about wrong colours etc. but I had a very big shop, and so had the room to display loads off. I used to have the back wall of the shop filled with ready made displays, and managed to sell loads of those. In winter I filled the dead hours just making displays up.(Small market town,LOTS of dead hours)
We had a wedding dress shop next door but one, and she used the bouquets in her window, so that brought me customers.