This is a better view of that outlet and the off white color of the trim works and doors in this room

Gorgeous cabs! i’d be tempted to do a tile in an earthy green (i’d move the outlet but that’s just a me thing)

I like la_la Girl's suggestion of an earthy green. Am not sure a white tile as I think you suggested would work as well with those very dark countertops. There appears to be gray veining in the countertops. Might suggest a light version of that for a backsplash color. Am not seeing large format tiles as appropriate though. Would suggest a smaller size tile. Good luck!

Move the outlet in and from my perspective a nice plain white subway tile. Keep it classic.

I would keep the outlet where it is and place the tile down the middle of it as the picture you show has the tile. It looks fine. I'd keep the tile close to the wall color and with a classic look for the style of your cabinets. Your cabinetry is beautiful.

Would it be possible to rotate the outlet to get it to one side of the counter?

I also like the look of a 6”-8” backsplash, going higher only behind the stove, or maybe use stainless behind the stove.

I don't see why you need 4 plugs there?

Gang up the switches, get rid of 2 plugs, move it all to the left, patch the wall ... electrical will no longer interfere with the backsplash.

Move the outlet. Check out Tilebar as they have a lot of options and send 5 samples for $5.

I would consider using a square tile. It feels more simple and old fashioned to me. Ivory, pale beige or white are going to be your best bets.

I would add soapstone around the stove and skip a backsplash everywhere else. Washable paints exist and what you have now is really pretty.

Love the cabinets!

Definitely Black, in keeping with the age of the home and style.

Would be a real statement!

https://www.wayfair.com/home-improvement/pdp/merola-tile-triplex-series-real-8-x-8-ceramic-patterned-wall-tile-eml10005.html

Separate the light switches from the outlets. The outlets can be 100% inside the tile work, the light switches 100% outside the tile work.

White tile would look good. Cabinets are beautiful.

"We’ve thought about moving vs. not moving the outlet for over a year, and are set on keeping it where it is."

You have created a really nice kitchen so far, there is no reason to skip a pretty easy step while it is still possible. @chispa and @apple_pie_order have given 2 great suggestions

Personally, I would consider changing the outlets that are to the right of the stove too. If you leave them as they are then it may be most appealing to choose a simple white backsplash that they blend in to or you could just put a short splash made of the counter material under the window, leave the rest painted and hang some art.

I’d look for a soft/light/warm tile to complement/tie in the flooring, cabinetry and counter.

I dont' mind the hanging outlet as long as there's minimal contrast between the backsplash tile and the wall color. Stark white is a NO for an old home, but a subway tile or square tile that's the same as your door/trim color would be very good. You'll need to be careful not to keep adding new variations of off-white to the space - so many whiteish tiles have a pink or taupey tone to them. You really need to find one that is either the trim color or the wall color - Daltile Restore Ivory from the orange box store is maybe one to check out. Get samples, hold them up by your door, probably something basic will be easiest to find the right color.

I recommend Chispa's or Apple_Pie_Order's idea. Whatever you do, don't just leave it.

You've likely spent a lot of time & money on a nice Kitchen, why ruin it with an obvious "make do" or "mistake"?

In the grand scheme of things, it won't cost you much money to change it.

If you are dead set against fixing the issue, then I recommend NO backsplash. Right now it's not too obvious of a "mistake" or "make do"; but if you try to tile around it (in whole or partially) where it is now, you will be accentuating it/drawing attention to it.

I like Jan's granite riser idea the best. Especially if you won't move the electrical. That countertop and matching rise look is so simple and elegant. And washable paint walls are actually much easier to clean than tile.