Old standby, white or lightly grey subway tile. With that era style of kitchen cabinets it would go well.

Beautiful kitchen! What colors are in the adjoining rooms?

Dining room is red. Here are a few options I like.

Here are some close ups. Counters are matte so I like the idea of a lil shine.

Mid grey to harmonize with the SS appliances.
I'd prefer a large format porcelain panel.

Would you do the decorative mosaic at all? Behind oven or sink?

the lightest grey (1st) of the group on the right is nice. Large format tile is nice, looks cleaner and less grout to catch dust and grease.

For me grouted backsplashes in kitchens are a mistake. Using grout near a cooking surface is short-sighted; you can't remove grease from grout, and over the years it will become sticky and discolored, and not very hygienic. Back-painted glass is gaining favor, it is functionally great, will never look worn or dirty like grouted tile, but limits you in future color schemes. I vote for a glass panel mounted on standoffs between cooktop and hood. Use standoffs that come off the wall only a little, then caulk the edges discreetly to seal-off the wall behind the glass.I'd leave the space between upper and lower cabinets painted in semi-gloss (oil based if you can find it). Both the glass and paint are clean-able, change-able, and functional. You can do decorative glass or mount a poster or photo on the back of the glass too. Very "personal" touch.

A foggy colored glass would look cool.

Beautiful subway tile;)

A subway tile in a herringbone pattern would be gorgeous in your kitchen- a different option from what Margo posted above (which is also beautiful):

3D WALLS WITH LIGHTING OR PAINTED

How about these?

You could consider wallpaper.

I love white subway tile in a kitchen. Unfortunately we had to work around a busy granite that was already in the kitchen so we went with a dark slate and really like it with the white cabinets. Your kitchen is beautiful! Carrera marble in a herringbone could be really pretty in your space.

Glass tile store: where do I find those?

Okay. It's in finally. But you will notice the alignment behind stove isn't in sync with the backsplash. Am I being too anal or should I let it go? It appears the lower cabs weren't measured to be perfectly in sync with upper hood ones. For as much $$$ as this kitchen is costing. Hmmmm. Thoughts?

Closer up pic.

Sorry to say, but I would have gone with herringbone subway tile. Given what you have done, I think it was a big mistake to put a different tile above the stove. It would bug the hell out of me to have all that off centered. I'd remove the insert and just continue the grey tile into the stove area. So sorry that you didn't notice this offset before doing the project.

I agree with Ramona and will add that the different tile behind the range distracts from your beautiful kitchen.

I would want something with shine and would avoid over-doing the grey. I know grey is all the rage right now, but I find it depressing.

it is very distracting. I would take that part out above the oven and continue with the same tile all the way across

Agree with Ramona.

The tile between the range and hood should either blend in seamlessly -OR- make a statement and be something dramatically & completely different.

What you have is too similar in color to make a statement on its own, but too different in pattern & size to blend in.

Here are a couple of examples of blending in the range/hood area:

And here are some contrast / statement ideas:

So, for best effect, either make the backsplash behind the range completely identical to the rest of the backsplash in the kitchen - or set up a total contrast / decorative inset / stainless steel backsplash, to completely differentiate the cooking area from the rest of the kitchen space.

The wall is painted. The art prints are mounted on rigid aluminum sheeting, and it's all under glass.

Wow - what an expensive mistake that was. I don't know if the cabinetry was not properly installed or the counter on the left of the range went too far, but either way, your range is not perfectly centered and you are stuck. To boot your tile installer should have seen this before completing the project and at least have you make a decision before getting the tile up on the wall.
IMO at this point in time, you have no choice but to rip out the insert behind the stove and make the subway tile go all the way across, and hopefully you won't notice the mismatch as much anymore.

I agree with most of the other posters.

Remove mosaic. Continue grey subway tile. Unfortunately the likelihood is one side of the backsplash will have to be removed because it will never likely lace in mathematically perfect.

It will solve the cabinet offset problem from a visual standpoint. It will go unnoticed.

The mosaic detracts from your whole kitchen design.

In regards to the alignment issue this is NOT an issue with the tile installer. This is the cabinet installer. From photos it looks like the filler next to the dishwasher is too big and a filler needs to be added somewhere between the cabinets on the right of the range to correct alignment. At this point it's nearly impossible to fix without major costs. This cannot be correctly solved by adjusting the upper cabinets.

If you want to add an easy to clean, contemporary element consider using high gloss acrylic wall panels. I'll include some pictures below

Innovate Building Solutions - how does the surface hold up to scratches? It's tempting, it looks great, but I've had acrylic table toppers and they all look worn out very fast. Ive used OTC buffers and surface scratch removers, but they don't really seem to do anything. How is your product holding up to wear and tear?

Cristina - this product is for backsplashes and shower/tub walls only (vertical surfaces). Surface scratches can be buffed out - I'll include a link below if you want to learn more about this material - it's got a lot of advantages - but like any material it has it's strengths and weaknesses:

http://innovatebuildingsolutions.com/products/bathrooms/high-gloss-acrylic-wall-panels

Your new kitchen is beautiful and I think you will be much happier if you just fix it now. I am in agreement with the others--the tiler should have noticed this before completing the inset but the way it is is now really ruins the overall effect of the quality kitchen. Remove it, remove the subway on the left side, and patch back in using the subway all across which will minimize the obviousness of the mis-alignment. It's so annoying when things like this happen, but this is life/the building process….and it demonstrates the value of a good designer managing a project; he or she would have either done troubleshooting earlier or noticed the issue at install and had it fixed then. (There is a reason the profession exists! ;-) )

Hmm, I'm afraid I couldn't live with that either. I'd be speaking to the contractor and asking for their solution since it clearly isn't right visually. Personally I'd take out the mosaic and run the subway tile through but as another poster said, the likelihood is that this won't match up perfectly either. Your best solution is to lift the work surface and take off a section and then shift your oven so that it is centred on the mosaic section but this is likely to be expensive and so the contractor will probably resist.