It gets a bit tricky, and I don't fully understand all the restrictions, but I do know that even buildings can be protected from commercial unauthorized uses. My understanding is that, in general, if you are not using it for commercial purposes, most everything is open game, but then there is the internet, and lawyers stretching boundaries of what is commercial. Being that you want to use names on products, I would certainly consult a lawyer before getting your pants sued off of you.
I would think that the big difference between your example of Destin and Seaside, is that Seaside is a private development while Destin is a (public) city.
...but, I'm not a lawyer.