Ok, so lets see if I can help you out here.
these are the sconces? 14" in an upward position? that should be fine.
Doesn't your fabricator have an extra piece of your quartz in a 2cm size? if it's a common color, he should. AND normally, those quartz countertops come w/the backsplash ready to use. Was this even offerered to you?
may I suggest you do away w/those taupe color mirror trim? I don't think they go w/your vanity or w/your more modern looking tile.
You could do mirrors like this
Or, get some wood trim (just a simple 2-3" width) stain it the same color as your vanity and frame out the mirrors with it.
(see the sconce height here?
here's another framed wood. I like the size of the wood frame, but not the grain.
this wood is a tad too rustic, so I wouldn't use a pine or Doug fir.
Try something like Alder (is that your vanity? alder? or a birch stained in a espresso shade)
Notice the backsplash height on all of these pictures.
However, if I had to choose something better, I'd do a cool tile.
Or, do the 4" piece up the back AND do a type of wainscot for that entire wall. It solves your problem of how to transition from the large tile
Here, tried to photoshop everything for you
Niche.
the preformed niche is fine, I just would have gone taller. visually I think the 12" is too small for that tall wall. But it's a personal preference. If you don't mind the look, keep it as is. it's too late to switch it now!
The Schluter metal Jolly piece is fine. I used it on mine (but it goes in first since it's anchored by the wall tiles.
here's a closer shot. (click on it to enlarge) I did the black, thicker jolly on the outside, and on the inside, back of the niche, I did a border of a thinner, gold Jolly liner.
You asked about the dry layout. I took measurements of the wall, and did a lot of math to determine where the niche would be and what the measurements would be. It fit between the studs which is why it's off to the right of the controls.
But there are no sliver cuts anywhere!
Here's the whole shower (if you click on my name and go to master bath redo on my posts, you can view the whole thing)
To get this herringbone design perfectly centered w/no tiny triangles, took 2 hours. here's the layout board.
Here's the surrounding subway tile. you can see the Schluter Jolly is in place (although they originally put in the wrong one! I wanted black. This was redone.
The cement tile wall w/the basalt liner tiles was a whole other design challange! lol.
Anyway, back to your niche. why not use diff tiles? or, what's going on the sides? just cut tile?
Here's one I did for my neighbor. subway tiles w/a glass mosaic on othe back of the niche. the little shelf is actually a piece of the quartz backsplash. (we used this quartz for the shower curb like you did on yours). this tile came w/a bullnose edge, so no need for a Schluter.
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mirror
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