I personally like the black. It is more dramatic and interesting. I think that a bathroom should be a little more exciting.

Can we see how a combination would look? Eg. One line dark the other light etc or in some sort of interesting pattern.

And play with it, dont stress,have fun! They all look nice but if you had to go with just one i would say the darkest one (1st pic)

The dark will likely show the sirt more. What about using he dark as a border? Also do you want a more modern or serene Feel?The bath tiles look so elegant so far - but then I personally like a marble floor.

The tiles on the walls and around the tub look great

I would use a completely different tile and go white matching the tub. I think this would be a better contrast with your wall tile

The grey tile is better but I'd still go lighter. This is a small space. Dark will shrink the room.

Pure preference. I like dark floors. When I go outside and look at the bare ground, it's usually pretty dark so it seems right to me. Not black though. There's a fine line.