I would use tile were it me. As to what type I would wait until the cabinets, tops and flooring are all installed and then chosse based on your home, other finishes (all together), natural lighting, etc., etc..

If you are piecing together the stone from leftovers then I would go with tile. If you want a slab backsplash of Taj then do it properly by obtaining enough slabs.

Since you’re electrical is already placed on the BS i’d do tile - we did a slab BS and placed the outlets under the upper cabs except 2 where we placed horizontally down low as that is where the coffee pot and toaster sit (that way you avoid hanging cords)

Another vote for tile. I love the look of slab backsplashes, but much of the finished look depends on the layout of your kitchen. For example, will the backsplash need to turn a corner, and if so can the fabricator line up veining at the corner with the perpendicular wall as well as the counter? You already have some seams on the counter, so getting a backsplash to line up could be a challenge. And la-la mentioned the electrical being in place, which is a good point.

There are beautiful tiles that would look great with your counter and cabinets. As millworkman said, wait until the counters are in before bringing home tile samples to view in your space.

Tile.

Can you give us more photos? I'm trying to understand what we're seeing - it looks like the upper cabinet is in front of the range hood, and that doesn't seem right.

I absolutely LOVE our Taj Mahal counters and full height splash, but it did take 3 slabs for our medium-sized kitchen. Because of our layout, the only seam (counter or backsplash) is on the back, next to the range. I don't even notice it. I spent an hour with the stone fabricator's layout expert, figuring out exactly which piece came from which part of which slab. The way the splash matched the counter was important to me, though once we started using the kitchen, that doesn't stand out as much as I thought it would.