Have you combined white porcelain subway tiles on the walls and Carrara black/white mosaic floor tiles?

I'm contemplating a Carrara basketweave floor (was planning a porcelain basketweave but found Carrara surprisingly only slightly more expensive), standard white porcelain subway tile (no Carrara on the walls), black trim, and I'm in need of inspiration, or rather, visual confirmation about mixing porcelain subway with marble mosaic floors.

Walls will be painted the following: from above the sink to the ceiling: a deep red, at sink height there's a substantial foot-wide wooden chair rail trim painted white, and between the chair rail and the baseboard, a foot and a half wide section that will be painted BLACK. It's a small powder room with a bathtub and no natural light. 8'x6'.

I'm going for a crisp urban contemporary look. Cavern, sexy, dramatic are more words that come to mind. It is echoing a contemporary black/white/red kitchen, while the rest of the house has a more earthy feel.

Any thoughts?