As you see in my second picture, the marble is on top of 4x4s. I put the pencil in because I thought it needed the line to define the two materials, and it mimicked the bottom of the chair rail detailing. What I hadn't counted on was that the thickness of the marble causing layout problems like you are anticipating. So, I made the pencil just a bit raised from the 4x4, so it would transition to the depth of the marble. I laid the 4x4 as normal and the marble as normal. The pencil, I laid thick to help with the transition. Tiling is a good exercise in humbleness. Nothings perfect and my tile job reflects that. I remind myself everyday as I see my tiny imperfections and remember laying this tile or that tile. The montauk is black and I got it at Home Depot via special order at 2.99/sf. It was 12x12 and I cut it to 12x6.

Believe me, I don't purport to be an expert on anything interior design, or otherwise decor-related, but I can say that yes, you should be able to mix them. It might depend on what type of stone mosaic you want to mix with your ceramic tile, but you should be able to do it. We mixed stone and ceramic in all three of our bathrooms as well, and they look terrific in our opinion. Not only that, but the sample board in the tile store that served as an inspiration for our guest bathroom, had a natural stone mosaic border with vertical white rectangular field tile (think "oversize" subway tile). We used a listello border (comprised of White Thassos and Emperador Dark marbles, and noce travertine sticks) and Daltile Modern Dimensions field tile in White (Arctic White?). Here are a couple of pics of our guest bathroom: I have to upload pics of the two recent reno's so I can post them. Will try to do so later. Both of those bathrooms have white field tile with stone mosaics, too.

Thank you everyone for your comments! We did a couple sample layouts tonight based on your advice, and we’re going to do the charcoal in the shower floor. If I can’t find a good quartz/etc remnant for the curb, we’ll do the large hex cut in half - with the darker gray grout we’re considering for the floor, I think it will look better than the white grout example I posted. I just can’t believe they are finally starting to do real work in the master bath - so much is changing in the house as a whole, but this is our biggest single room project with all new materials and design elements. Exciting and terrifying all at once!

I think these sorts of ideas work best with more than 2 variants in use. Sometimes 3, but I think at least 4 shades makes it look rustic and intentional - rather than just one box was wrong. Antique delft solid tiles. Lots of shades: Sometimes the tiles themselves vary in shade across the tile, as well as between tiles: More dramatic differences, but only 3 shades that I see: More shades, more subtle shading, and crackle: