I create custom posters and feel that surprising them with a poster of one of their pieces would lead them to say oh that is cool and lead into a conversation that may result in a client or client reference...is that too much on the first date or should I be happy with a bit of feedback and to have gotten time in their mind regarding the product? In the past if I ask to take a picture everyone says no and if I just do it and bring in a print they are happy and don't mind.
As a business owner I also feel that for someone to come in and take pictures would feel a bit violating. We've actually had competitors come in and take pictures of our store layout in the past in order to copy.
If you're trying to get their interest with a custom poster relevant to their business, why not use stock footage? For example, I am pretty sure there are plenty of hookah images you can find for free or really cheap and then making it into a poster would give you the same results.