Nic's,,the 4" piece should come off easy enough. you may tear the paper on the backsplash, which is ok if it's not too deep into the drywall. I guess if you were on scene you could have asked them not to install it. I mean, what difference is it to them whether or not it goes on the wall? to say it would be more money not to have one, is ridiculous. it takes more time to cut one and finish the edges! but, whatever. as for the design, it's a herringbone. and those I've shown you come on 12" sheets so you don't have to do the actual design (which is very difficult) the first one is calacatta marble in a 1x2 herringbone (also comes in a 1x4, which I like better). You can find this all over,,,even Houzz carries it. If you want the marble, then stick w/the Calacatta not the Carrara. carrara is a blue/white and will clash w/your counters. calacatta has a warmer tone to the stone. the 2nd on is a tumbled travertine which you can get here: https://www.pebbletileshop.com/products/Cream-Herringbone-Stone-Mosaic-Tile.html#.WhX_BLaZNT4 this will give you an idea of what it looks like installed (you can turn it longways as well) If you search "herringbone mosaic tile" you should get lots of ideas and places to buy them. this one is from Lowes, allen and roth. you could buy one and bring it home to see how it looks this is the basketweave this would also work. crackle glass by Merola tile. Olean Glass mosaic. I think Home Depot carries thesenothing wrong w/doing a little color. pale green, blue or gray would also work well. https://www.homedepot.com/p/Merola-Tile-Chester-Sage-3-in-x-12-in-Ceramic-Wall-Tile-1-sq-ft-pack-WNU32CSG/300341310 these would also look nice,,,they have them in different shades https://www.mercurymosaics.com/shapes/field-subway-tile/

I would not do brown (but I am not a brown person). I would probably either continue the countertop up or do a white or gray subway tile backsplash (see photos). I prefer a light backsplash color and nothing too busy, especially with your countertops. I just removed a busy backsplash from my kitchen and I am so glad to see it go. Our replacement is going to be very simple, most likely I will bring up my counter (which will be a marble-like quartz). But my design aesthetic leans transitional/modern, and yours may be different. Good luck, these are such hard decisions!

Thanks @J Inhof and @Pam A. Good question about the tones of the Pure white - I don't have a sample of the Pure White (oops!) but I did look at it with my cabinets in the IKEA store (which obviously has very different lighting). The Pure white, was very very close to the cabinet color. The Frosty Carrina overall read a slightly cream - I do have a sample of Frosty Carrina, and in my kitchen it also reads slightly cream (and the website describes it as ivory). Here is a photo I took at IKEA of 'my' cabinets with Frosty Carrina:

101streitired. looks very nice. could I offer one tiny bit of advice? thanks! The window. what you have is all very white and very solid. the mini blind is my pet peeve over kitchen windows. let me show you a photo shop of a new window treatment, and possibly a sconce. ( realize you can't do a pendant, and I know you have the trim piece across the front. but at least look at the window treatments) don't be afraid to add some cutting boards and greenery to the mix either