Why not just carry the marble hex into the shower? At 4x8, I am afraid that choosing a different product will visually chop up the space, making is appear smaller. Using the same product on the entirety of the floor will do the opposite.

Otherwise, you can choose a plain white hex the same size.

Jbax, my only hesitation is the maintenance issue of using marble in the shower. I've seen some horror stories on this forum from others who have done so, and I'm afraid to risk major issues (like discoloration) and have to re-do the whole thing! This doesn't worry me quite as much on the bathroom floor, since we'll have a bathmat.

Look at Daltile Keystone mosaics for a number of gray shades or white in porcelain

I had the same dilemma (love marble hex; didn't want to deal with maintenance in the shower). I prefer the calmness of continuity (1 tile) - so went with white porcelain (ceramic? not sure) 1" hex tile with gray grout for both room and shower floor. Love it. You could do that, and then use marble for the countertop and shower jambs (which is what we did - no tile grout at the jambs/under the shower glass) and shower niches' edges (we did that too).

ap999, that is probably our backup option. Glad to hear you loved the outcome!

You could go with a solid shower pan. in a nice matching gray or a white. In your space it might work wonderfully depending on the layout. I have a 3x5' cast iron shower pan in a very light gray. they come in 4x3' too. Or get a solid surface manufactured one to meet your needs. In my 5' long pan, I used french shower doors, so I only drilled into the side walls for mounting. I love my french doors, both open and swing both in and out.

http://www.us.kohler.com/us/browse/bathroom-showering-Shower-Bases/_/N-2d8r