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.
It's often easier to gain a new client by providing concepts or proofs up front (if you can afford the time and expense as a marketing cost) rather than attempting to explain what you "could do" for them. You do seem to have answered your own question in our explanation. If you've done it with success, why alter your approach? You have validation from your own experience.
Many creative-field freelancers use this technique to score new clients and gain referrals. A word of caution, however - public spaces like a hookah cafe are one thing. Private facilities are another. Expect at some point to have it demanded that you turn over the images or have someone refuse to allow you to "use" the image(s) in promoting your business if it includes their brand or IP in a manner they don't feel is consistent with their brand identity or implies an endorsement.
Feel free to reach out with any other growth hacks you're considering. I'll be happy to give you a quick thumbs up/thumbs down and why.