If you're going with just a concrete floor, you could go with an acid stain concrete floor. There's some that are done extremely nicely. I remember years ago the architecture firm I was working for had a lunch and learn with a company called Skookum Floors. The only local flooring same they had done was the Duek on Marine Drive...it was a gorgeous blue floor. Here's some other sites with concrete floors.
http://www.concreteideas.com/
http://www.concrete-design.com/