The floor tile from the store display looks like it would work.

You mean the gray would work well?

The grey would allow the bossy shower to stand out nicely.

The grey will date your floor, and the white/grey is too busy with your shower tile. Your room looks like it is on the smaller side, so I'd find a plain white that matches your marble.

James Overton. Do you mean white matte on floor?

White 4" floor hex in a similar tone as the white in the shower tile.

Is your shower the same size as that in the inspiration pic? I'd order more than you need, hand select the least bossy tiles, and label the arrangement and direction of each tile in your shower. The pic looks mellow but the actual tile sample is much bossier and could look very different than the pic. See the lower left side under the bench? Your whole shower might look like that. You might be ok with that, or disappointed in the end.

The black on the board.

From experience : < { with your smaller footprint see if you can do the floor with less grout lines.

Update: finished! Went with black octagon tiles. We love it