I don't have any specific tiles in mind, but I think a concrete shower floor would look really nice here.

Does the manufacture of the shower tile make a dark gray tile? A darker floor in the shower would look nice with the light gray floor tile and shower wall tile.

I wondered the same thing as Jean. The tile looks to have texture which would be good on the floor.

what would FEEL good under your feet? In general I would go with a lighter color than the walls. But really pretty idea!

There are loads of porcelain tiles with non-slip texture that would work here. Random cut slate (about 3x3), teak slats, or like alenm3 suggested, concrete could be awesome.

@Jean Benelli, @emmarene:

The tile does have a texture to it and would be good for a floor tile. However, the only darker color is black.

http://products.daltile.com/series.cfm?series=315&item=4637&;

The alternative would be their lighter color, White Ritz.

@Jeffrey: Thanks for the other suggestions. I also considered teak, but the higher maintenance is somewhat of a disadvantage I think.

Concrete would be interesting. I guess the hard part is imagining how this will all mesh together in the end.

Given the available tile sizes in 1x2, 2x2, and the different pattern suggestions on that site, maybe we could do a mashup of the Gray Shimmer/White Ritz tiles to come up with something that keeps the tile textures more coherent (from the bathroom tile, wall tile, to shower floor tile?

What a shame, I don't think I would use black. Too dark a contrast. Can you find a smaller mosaic tile in a darker gray?