If your counter tops are not level, you need to get that corrected before moving forward with any back splash tile. The counter top won't break if you have someone level it. Whoever installed it for you should come back and fix it at no cost. That is a significant mistake and shows a lack of attention to detail and questionable professionalism. It means that objects will be able to roll across or off your counter top. That's not how they are supposed to work.

Counters are not level because cabinets below them are not. The cabinets were there when we moved in and we had the counters installed after we moved in...

Backpainted glass would work.

Wow! That's great to know you found an installer who made it work. Are you located near Cleveland by chance? haha.

Mark_rachel - do you recall what your slant was? 5/8th or worse?

The weird thing is that the clearance between counter and upper cabinets is 18'' the entire way accross (with small variances +/- a tenth of an inch) so the upper cabinets were basically installed on a slope as well.

I can take a pic tonight & measure.

Mine is not obvious to the naked eye

If you can get more of that pretty granite, you could use that--if not everywhere, at least behind the range.

My cupboards were wonky/uneven too and I was still able to use subway tile. I just adjusted the difference at the top where the wall meets the cabinet. There is a bit of a gap in one section, but I filled it in with grout caulk. No one will ever see it unless they are specifically hunting for it.

Right under my micro is where you can see the grout line change. Under the cabinets he just cut the tile right up next to the cabs.

If everything is at a even slant/slope than the tile should go along with that. It should be installed to match the countertop. That’s where your eye will go.