Visually it really comes down to what the tiles look like. Some tile series follow the stone pattern with large plain sections and the the bold veining that is characteristic of the stone; other series are more muted. Given your floor size will you like the variation? I used a 12x24 on my walls, but the 12x12 on the floors in my master (not a marble pattern). Which line are you looking to use?

Not a fan of putting polished stone tile on the floor if it's 12 x 12 or larger. You could get away with a polished stone mosaic tile, e.g. a basketweave or herringbone pattern, since the grout lines will make it less slippery. Go with honed, or change the tile format.

Is this a tub/ shower bath? Or just a shower?

If a shower? Mosaic on shower AND bath floor. It's too small to make it complicated

The master bath will always have throw rugs so that you are not stepping on to a polished tile. Helen, are you talking about a bathroom without rugs on the floor being slippery? Skippack Tile-this line does not come in 12 x 12. The tile look is like a marble with veining. (Marvel)

both master bath and powder room bathrooms are tub/shower.

I have 12x12 polished tile on floor in bathroom. There's no problem with it being slippery, but I also keep rugs down. I do prefer honed....I have that in my kitchen and it shows less wear. MIL is 100 and her walker's starting to wear polished finish.

Yes a rug or a mat will make it not slippery provided you STAY ON THE RUG. If your feet are the least bit damp, you will slide if your feet move off the mat.

Also I got rid of the bath rug/mat in my new remodel because I love the clean lines of my beautiful new floors and it is one less thing to have to clean around. I don't understand why one would have a rug if one has a beautiful floor - especially since you have relatively little floor space. I also have a narrow urban master bath and so the less visual clutter the better. I designed my floors to be beautiful and I love looking at them :-). FWIW, my master bath has Calacatta marble basket weave floors and I really love how they look. I love the warmth of the gold as I am not a fan of the gray/white Cararra marble look.

I had a mat in my old bathroom (prior to my remodel) and 12" x 12" vinyl tiles - the old kind with the black and white checkerboard pattern. My cleaning lady moved the mat and I stepped out onto bare floor and skidded - luckily I didn't break anything.

So then what type of modern floor would you install in a small bathroom with calacatta polished walls. I don't like mosaic or small tiles with lots of grouting. (That's what I have now). I chose a faux wood ceramic for floor, greyish white (12x24), but my contractor says it doesn't match. I don't want to go dark because the room will look dark and dirt will be more prominent.

It does not have to be a 12x12 tile for the floor, it can be 12x24. It comes down to the look of the tile. Your floor (3x5) would have 8 tiles in 12x24; how much variations do they have as you have a limited amount to work with? Will you like how the veining lays out? Without seeing your selection, it's hard to guess. For a modern look, you can also consider a more solid gray tile that matches the grey vein in the wall tile.

@Stephanie, I agree with your contractor. What you could do instead if you don't like mosaic tile, is a dark gray slate tile, which is less slippery due to the texture of it. I'd do a herringbone pattern with tile that's roughly 4 x 12, or your could also do a 12 x 24 in an offset pattern. See below (the bottom photo shows the 12 x 24 in a kitchen, but you get the idea):

Koopman Bath · More Info

Park oak · More Info

http://www.nemotile.com/tile/product/marvel/ that's the look on the wall. I'd be fine with the veining on the floor I think. I hesitate getting a gray floor tile because it will show dust specs. It would have to be the right color gray.

Your selected tiles are fine; they do not have a bold vein pattern. They look fairly consistent.

Try looking at Happy Floors tile... don't know if you have access to this brand. Alot of their tile is rated for pool areas - that would mean less slippery. They also have great patterns bold and simple!
Best of luck!