You used the quartz for some of the backsplash so now for behind the range I would go a simple gray subway tile with matching grout in a gray that works with the counter or simlpe gray back painted glass.

I think a glass tile would look lovely. You could use gray, a soft blue or green. What colors are you drawn to? What are the color# in the adjoining areas?

I'd pick a creamy white subway with a light sand tone grout to work w floor tones. Pick a stylish hi arc faucet with that opening and visibility there. You still have counter top items to place in and there is room for a smallish work cart it appears...[I'd want one] and of course floor mat or runner when you get to it for some pattern or color. I think a subway tile but texture or a slight change of size from the "usual" would be enough interest if you want a little something [I think basic suits the space, tho] ...... here are 2 carts/ I'd be searching for one if this were my kitchen..... [assume an island wasnt going to fit] .....counter and floor look nice w cabinets by the way.

Sonoma Kitchen Cart with Drop-Leaf [Barnwood Wire-Brush] · More Info

Urban Industrial Loft · More Info

You already have the quartz under the pass through. I'd continue that as a backsplash, with the caveat that you find a sheet of stainless to sit behind the range and avoid scorches.

But I wouldn't tile UNLESS you take away the quartz under that opening : ) and run tile there as well.

In that case? Get yourself to the tile place local, bring home some selections in white, and use the PALEST POSSIBLE gray grout, or white.

PS....... That quartz piece under the pass through should go to counter top edge/wall junction. . So that's a do over......if you do quartz. Nor should you pay for that do over.