Beautiful kitchen! 4" square tile would be both MCM and simple and classic.

have you had thoughts of keeping it simple ? I sure would.... kitchen is smallish..there is adequate detail w ceiling and beautiful wood. I would stick w a white subway ..but there are variations on subway tiles now.......a little texture / a different size tile/ ....you can lay them upright...and so on.... If you REALLY want color....Id look at light sagey green....very complementary to the wood in your space. Bring in various samples.... and let folks comment to help you narrow it down.

various green tiles in similar spaces...

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2x2 porcelain , 3x3, or 4x4 would all be appropriate.

I like the zellige tile idea.
This is such a beautiful kitchen!!🖤🤎🖤

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Ohhhh what do you think of this one? I’m loving it!!

https://www.tileclub.com/products/luna-arc-white-4x4?variant=43084606767255&utm_source=google&utm_medium=paid&utm_campaign=18135023935&utm_content={adgroupid&gad_source=1&gclid=CjwKCAjwnv-vBhBdEiwABCYQA4zLeLF607J2J57SxQgIDVhBsRHs5y5oFGynDK3M5QoHycyhuB5MCBoC5JwQAvD_BwE

The matte Arctic White in the 1x3 lattice pattern would be great with that! https://www.daltile.com/products/Wall/Color-Wheel-Mosaic/Matte-Arctic-White

Or, the chevron. https://www.daltile.com/products/Mosaic/Color-Wheel-Retro/Matte-Arctic-White

Different kitchen but I did a pale pink mosaic backsplash in this kitchen to reference the pink terrazzo flooring in other parts of the home.

How authentic do you want to be?

I feel like a lot of "MCM" items, including tile, are really 21st c. revisionist fantasies, not really what they would have actually done at all. (Like even the historic reproduction tiles would rarely have been used as a kitchen backsplash in an ordinary modern house of the period).

There's nothing the matter with doing the 21st century version, it's just a thought to consider.

House is from 1966. Only thing carried over were pendant lamps. No backsplash previously.

I love your cabinets and the Herman Miller Bubble Light! Have you considered using the same material as the counter for your backsplash. Many homes in the 60s had Formica countertops and had either a 3" thicker backsplash or continued the Formica sheeting from countertop to cabinets without any backing.

Heritage Tile has a Zen+Clay collection that has lots of options to infuse some texture and organic feel to break up the solid surfaces/clean lines while keeping things streamlined/clean. A nice glass tile can also work well with your cabinetry choice (which is gorgeous by the way).

If this was my kitchen, I'd probably be opting for a single piece of acrylic or glass for the entire backsplash to keep those clean lines of the upper cabinets (in a barely tinted white tone) - a version of this.

I agree with @palimpsest. To me, the most MCM of MCM houses is the Miller House located in Columbus, Indiana. The home was designed by Eero Saarinen and completed in 1957. Here is a photo of the dining area and the kitchen - note the tiny brilliant turquoise backsplash tiles.

For fun, here is the Miller House living room, with a sunken conversation pit and groovy steps down into it

White splash for sure - either a 3" of your counter, a white ceramic tile, or glass over your white wall. You have a great thing going with your white and wood look and I wouldn't ruin it with a color, not even a subtle color. Pay attention to having a wood ceiling as well and how that brings enough warmth, color, and texture to the room without needing it in a backsplash.

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I also love the idea of no splash.