Have you spoken with your customer about this? It's their business so how do they see it ?
If you speak with the customer & ask them what they like/dislike then you can often get a good idea what direction to take & their is a better chance that they will like what you come up with
Just my opinion but I believe that the customer should have some input into the design of a sign for their Business, after all they are the ones that have to live with it once it is done
I normally ask a series of questions to help me get a better idea of what they really want.