of the four selections, I like the subway or the diamond selection on the left. With the subway you could insert a square of basketweave design under the hood, or something similar, that you like.

Another vote for the marble subway! Also, take a look at this waterjet cut Carrara (like this beauty I fell in love with: http://allmarbletiles.com/tile-collections/bianco-carrara-marble-1x2-polished-3d-waterjet-mosaic-tile.html) to bring in as an accent tile for a little geometric edge. Your cabinets are beautiful; which brand and door style are they? And I love that leathered steel gray countertop!!!

Pick whichever one matches that cuty pie standing on the (very pretty) floor.

Grout certainly changes how it will look. I've attached a photo showing another convex pattern for illustration. You could grout yours on a sample board to see what you think? And out of curiousity, have you tried it horizontally? I like all your choices. What a lovely kitchen!

BTW, can you tell me about your convex diamond tile? I'm in backsplash search mode and my granite is going to be similar to your island.

Another vote for subway tile. If there's one thing I've seen over and over on this site, is that backsplashes certainly can be too busy, but they can almost never be too simple. The most beautiful kitchens on here, the ones that get the most across the board ohs and ahs, have really really neutral backsplashes. Go with the simplest.

I'd go white and bright with that dark floor and counter. If you do the diamonds, I'd go with the white, run horizontally. With white grout, it will have a subtle quilted look. Very nice tile.

I don't like the marbles with the splotchy granite. Too much of the same thing.

Herb ~ I thought about using an accent behind the cooktop but I'm not sure I like them! I really like the diamond too.

Philo ~ I'll look at the waterjet tile tonight, thanks for the link! The cabinets were custom made by a local shop. I went with a 3" stile and rail and absolutely love the look. The leathered steel grey is even better in person ;)

Barncatz ~ The first thing I learned on Houzz... everything looks better with your pet in the pic! Great idea about grouting the sheets... I wonder if they sell small samples? The convex tile was purchased at Arizona Tile and it's priced really well so using that would save me a ton! We put it up horizontally and vertically, I like it horizontal.

H202 ~ Do you like the marble subway or the plain tile?

Nosoccer ~ I love the look of that light grey grout.

Mayflowers ~ Would the white diamond be too much pattern or should I be looking at texture vs color?

I think with white grout this would look great.

sumjay- I'm pretty certain that I just used the left-hand diamond tile in my master bath as a large framed-out accent. It's a new house, in progress, so I'm not there now, but will be either tomorrow or saturday. I can certainly take a photo & post it here. Maybe that will help you with your decision :)

I like the bright white diamond also. I'd do a mockup with matching grout & see if it has the subtle quilted look that Mayflowers described. That would be pretty. I also really like nosoccermom's & barncatz's inspiration pics. Either would also look beautiful in your kitchen although I believe the tile barncatz posted is pricey.

What an adorable little pup. Scrolling down & seeing him made me smile. He contrasts beautifully with your floor.

Another vote for the marble subway tile. I think the simpler the better but the marble will add something special.

Would the white diamond be too much pattern or should I be looking at texture vs color?

No, not too much. You need pattern. Every shape in your kitchen is rectangular and simple, from the Shaker cabinets to the floor tile. That's why you don't want to add more rectangular shapes with subway tile. With white grout, it's all about texture. I think the pattern will blend like this example. I think this is an iridescent tile, but it's the closest example I could find. Try grouting it like romy suggested.