Herringbone is a classic pattern, as well has hexagon.

I have marble in one of my baths, and although we use a sealer that provides traction, it still can get slippier, especially if you forget to do regular maintenance or a little soap gets on the floor. We'll be replacing it in the next remodel. The smallest mosaics with the grout lines that Beverly27 showed provide some natural traction; another bath has these and there is no issue.

Beverly, Thank you so very much! I do not care much for the herringbone designs as they seem busy to me but those small hexagons are really nice. Perhaps, I could frame a field of those hexagons in the middle of the floor with some polished marble strips along the sides of the room so I could still get a few polished marble strips in there.

Gooster, thanks for your comment on your own experience with marble flooring. I think I will definitely look to doing something safer now that I have confirmation. And Beverly gave me a great option!

I'm wanting carrara subway tile in my master bath when the build it... and I'm considering a grey rectangular tile. Not sure yet. I've gotta do more research, but I do not want marble on the floors either. I have the same fear of it being slippery. Also, I think it's pricey and I worry about maintenance and it looking dirty too fast. I want to make my life easier. I'd love to know if anyone's used an alternative to marble on the floors to go with marble shower tiles?

The 2" imho provides more traction; I have the basketweave type and the grout has held up well after 18 months. But it doesn't get daily bath traffic, but lots of other foot/shoe traffic (main bath downstairs). With regard to soap, I should have said slightly soapy water. While soap is an issue on any floor, I think with polished marbles it is magnified about 3x. (Ours are 12x12) There just is no traction at all -- even a puddle of plain water can be slippery if you don't keep up with your sealant. And even then, those with fragile balance may have issues.
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Zoe52, you might need to create some type of break between the inlay and the 18" tiles to allow for the difference in overall color. Here are some examples.

I've had polished carrera floors in our MB for 8 yrs. I think they may be 16 or 18 inch. Can't remember. I have not had any issues with slipping.
They do eventually etch and the surface will eventually get duller. It gives them character. I still love them as much as I did the day they were installed. They are timeless.

I love that Greek Key design. I have it on the black border of my kitchen cabinet molding, on the rug on my living room floor and I just bought bath mats and will get towels with that design. It's so classic looking and modern, yet traditional (if that makes sense). Here's a photo of the style of bathroom I'm going for. I decided I'd like to be different and use slate with the carrara. If the contractor doesn't talk me out of it.

Over in the bathroom forum there was a discussion of porcelain carrara look tiles.

Here is a link that might be useful: Carrara tiles honed and polished