Add in a 2.5 white marble mosaic border. White marble threshold and door casing. Concerned the floor isn’t cohesive and too segmented. Thoughts?

Is this in your shower? It's hard to tell what's going on in the photo.

Again, not sure what the question is. I see the small dark gray floor tile, then the patterned tile and then the large marble or marble looking large tiles. Lose the patterned tile, or the large format. You have one too many things going on. I'd lose the patterned tile as it is already going out of style.

The photo seems to show small dark gray mosaic tile in a future shower enclosure and a gray-and-white patterned tile which will cover the rest of the bathroom floor. Are you asking if you can put in a white mosaic tile border and a white marble threshold? If the white part of the patterned tile is marble, I would say “yes”. I would prefer no border, but the white marble threshold should match the white part of the patterned tile.

Is your shower and the rest of the floor properly waterproofed?

The way you have it laid out now looks weird.

if the floor isn't that big, then just do the entire thing in the mosaic flower tile.

If you want to use the really large gray tiles, then do a 'rug' insert w/the flower tiles in front of the vanity

as for the solid shower floor tile, make sure you stagger those sheets so you don't end up w/grid lines (Personally I'm not big on the 1x1 squares for the shower floor, but that's me. ) why can't you use the flower tiles for the shower floor?

Another vote for shower all in flower tile. And floor in large format tile.

Stay with the shades of gray tile.

FWIW the flower tile is already out in the NYC area. How about a larger square of hexagon tile on the shower floor so there is not so much grout, and then use the larger marble/look tiles for the rest of the space.

You should pick either the flower tile or concrete look. They don't work well together.