One of the things I liked architecturally about First Jefferson Unitarian Universalist Church, Fort Worth, was the floor. A tinted, polished concrete floor that (appeared to) wear well, made good use of resources and didn't fight with the modern design of the walls and ceiling.
I thought then and now that if I were in an urban building retrofit-as-church building, I would do worse than having a sealed concrete floor. (Yes, that's the kind of thing I think about.)
And Apartment Therapy has an article about it today.