Your color palette is the same as mine on the remodel we are about to begin. I went today and picked out Mohawk Trapani tile (12x12) in Charcoal with pewter grout. It looked really good up against the lighter vanity top and white wood. I will also have white toilet and tub and wood work and the darker floor seems to ground the room and make the white pop. I have had a really hard time finding a grey tile I liked that didn't have blue or green in it and wasn't slick when wet. I didn't want white tile because this is our main bath and used by my two not-so-neat teenagers. Hope this helps!

I am going with a similar look and am doing a carrara & nero marble basketweave faux rug for the floor. I will probably have darker bardiglio tiles around the edges of the room and there will be a cararra twisted rope border (and nero liner tiles on each side of the rope) to delineate the "rug".
This way, the pattern does not overwhelm the room and it is a very pretty look in and of itself.
I wish I had a mock up of it because even dh has not seen what I chose (other than the basketweave middle), lol.
Oh... and am using dark gray grout because white would be just plain suicidal in our house.

Maybe Bill V has done similar and has a pic?

You could also do a black and white floor. There are several patterns that you can choose from: Daltile pinwheel, The Tile Shop plaid pattern, a carrara basket weave, a hex tile, just to name a few.

Here are some pictures of my finshed bathroom. My counters are white carrara. Floor is all white carrara marble too. The border is 6X12's polished, the inside is the honed herringbone mosaic. Grout is Misty Grey.

I used carrera in the shower and vanity counter. I wanted to dress this down so I picked a floor tile that did so. It is Ergon Elegance Bocciadarto grey. I think these two look great together. They are being installed now so I'm excited to see!

We have some dark brown wood-look plank tile with espresso grout in our kitchen, which has predominantly gray and white cabinets/countertops. I feel that the dark color makes the floor 'disappear' a little so the focus is more on the cabinets and countertops, and the room is less monochromatic. It also adds some warmth into what would otherwise be a visually cool room.