Post on the Bathroom Forum. There numerous threads on building a good shower. Good luck!

Sounds like a fair deal. Heated floors are awesome! And glad you've had conversations with tile guy. Sounds like you're in good hands. OK then the easiest thing I'd recommend would be to find something else for the shower floor itself and just eat the difference, if it's a pain to return the marble. Pick another floor for the shower, but not one that tries to match the marble hex. Things want to be either exactly the same, or different enough that it looks intentional. Glad you like the wavy subway! I think it looks great with marble, which is what I used to trim out (jambs, threshold and niche.) Happy to share pics if you're curious ;-) The only reason I mention the non-white colors is that I found it almost blinding at first, with the high window and the lights not yet on dimmers. I was used to the slate sucking all the light out of the room. There's also a matte version of the white (Cloud Matte,) which is quite elegant with marble. At the risk of being a Debbie Downer, don't do the marble inside the shower, unless your tile guy feels super confident about it. I don't want to see your name come up on this list of unhappy people: https://www.houzz.com/discussions/query/marble-shower-floor

I like plain 12 x24 porcelian tile for the main bathroom floor and the shower walls. Not sure what you mean by pony wall and where that will be .If you post a floor plan you will get much better help. an 8’ shower is IMO too big to ever warm up in the time of a regular shower. What is the wood look tile for? Where are you planning the accent tile to be? I need to see a to scale floor plan with maybe on just the fllor plan and the other with what you are planning.Mark all windows droorways and the plumbing at least for the toilet unless you are planning on moving that , which BTW is expensive . Mark all measurements clearly and I suggest you use graph paper it makes scale easier to do. As for all the tiles you have posted please label them as to where each will go. What I see of the bedroom looks very rustic , is that the look you want for the bathroom, maybe post pictures of the bedroom since IMO the 2 spaces should be in the same general style.

I would do a running bond horizontal. The striations, IMO, pretty much lock you into horizontal, as Patricia Colwell Consultingsays. I would also consider ditching the pebbles and going with the mosaic that matches the wall tile. the cohesive design element will be calming. And - I also worry about how the pebbles actually feel and hitting it wrong with my heal and it being ouch-y if the grout is at all recessed. ALSO - I HATE seeing the edges of the sheets or a grid pattern on a floor. Drives me insane. Figure that's much more likely with pebbles than a square or rectangular shape. And - FOCUS ON WATERPROOFING - the best / most gorgeous tile in the world won't protect you against water damage from poor prep