I suggest the NEM foundation offers free stickers to merchants that want to accept XEM so they can stick them on their windows.
Maybe have a regional representative that ships them to local merchants to save on shipping.
Also a list on the Nem website that is searchable by region. Let’s say I am in New York and I want to spend XEM, I should be able to search NY to see where I can go to buy a pizza or a drink with my XEM.