Here is an option if you prefer the checkerboard design using 2 different tiles. I think they would work nicely. The Ebony Marble design is forgiving in colors used, not too black and solid. The white in it might be a soft white, not too white. Maybe samples would help. The size tiles and dimension thickness would have to be the same. I did not verify these. Ebony Marble https://www.lowes.com/pd/Style-Selections-1-piece-12-in-x-12-in-Ebony-Marble-Peel-and-Stick-Vinyl-Tile/999978538 The Crescendo might lean to an off-white. Crescendo https://www.lowes.com/pd/Armstrong-Flooring-Crescendo-12-in-x-12-in-Groutable-Marble-Look-Peel-and-Stick-Stone-Look-Commercial-Residential-Vinyl-Tile/1001435690

Id make my decision in this order. #1 quality and flatness of tile (this will decide if i stagger/stack. It will also decide how tight of a grout joint i can actually use .) #2 layout for best fit in the given space( accounting for expansion joints/grout joint size) #3 focal points (I.E. am I placing a recess niche in the wall? are there any windows i want balance with etc etc etc. Dont skip #1 #2 and dont force either/other. still make sure you nail #3

Design-wise, it just depends on how it looks. Usually it's shiny on wall, matte on floor. But it doesn't have to be. Show the tiles you're considering and...well, people will probably STILL ignore your request and keep saying it's too slippery and not answer your question (even though you are aware of that and I think it is safe to assume you will not use it if it is not suitable in that regard)... anyway show the tiles and see if that helps people decide. There are normal things that are done, and you're not doing it the "normal" way, but that doesn't mean that your particular choices don't work that way.

Looks like the OP has that wall tile around the shower threshold and, I assume, the walls too, so not that easy to get rid of the wall tile. Maybe just reducing the amount of the wall tile, except for shower area, will help tone down the discord between tiles.