Can you find out what the color is in your inspiration picture? If so, thats the color I would go with. It looks very nice with the agate backsplash.

Hague Blue by Farrow & Ball. It has green undertones that I’m not sure will work with this agate. But I’ll check out the LRI and look for something similar.

What material and color are you using on your floors?

Flooring will be medium brown LVP:

https://www.flooranddecor.com/optimax-flooring/anthem-alder-eco-resilient-flooring-100887025.html

Really? I’ll get a sample and try. This is definitely out of my comfort zone but I love the idea of a bold room. Hard to be bold and also scared to make a mistake.

or any color from your countertop

My dear, you are already bold in choosing that fabulous agate backsplash! Keep going in that direction! And please post the finished room!

Celery, thank you so much for the mock ups! These help immensely. I love the dark blue. Was able to show this to my husband and convince him to let me try.

Ptreckel, thanks for the encouragement! I’ll definitely post the finished room.

I like the dark colors and in a small powder room it works. Definitely go dark and use a matte finish.

Are you going to center the vanity? I think it will look better even if you have to move plumbing a few inches.

You might also consider painting the vanity in that dark color and keeping the walls light.

are you backlighting the agate? (I thought it was going to be your countertop but I just saw it's for the backsplash?)

see how they backlit this one?

this is countertop, but imagine backsplash. is the vanity you're using that white one?

btw, with white and light walls, it just doesn't have the same impact as the dark color

and please say you're doing a wall mount faucet??!

here are some deep navys, and some blue grays.

I also had a bunch of colors saved for this slate tile. these are all slate blues and steel color blue-gray paint colors

are you doing the blue vanity too? would be cool if you floating a thick piece of the agate.

I'd go bold in the powder room. bold and dark.

what do you think about doing pendant lights? You could hang one in the corner or over the toilet

Is the sink going to be white? Do I understand the agate will be backsplash only? Blue will be beautiful if there is enough blue in the agate. The predominant color on my screen is gray. So perhaps a blue gray might work too? Here is another option. More blue gray. But if you are doing full white sink and countertop then that blue could work. Just do samples. I love deep blues and just did my dining room in a deep blue. So just think about it.

SW Outerspace has an LRV of about 14 so it is deep and non-reflective. It’s DNA has it at 255 degrees on the color wheel which puts it in the blue/purple Hue family. It leans more to blue and is cool so it is worth a sample to see how it looks in the light of your room. I would also be tempted to paint the vanity the same color of that is the vanity you are using? Is the commode across from the vanity?

so here's a photoshop w/the agate as a backsplash with a wood vanity and those dark blue gray walls. with the gold pendant. I actually like it w/this wood color

Maybe try Hale Navy or Soot. Both really pretty.

Downing slate would look great with it.

Your backsplash is stunning! I didn’t know there was such a thing — where did you find it? Can’t wait to see how your PR turns out!

I think the blue grays are stunning. Lots of great ideas. Beth’s wood addition is brilliant too. Going to be stunning.

Beth, I love the wood vanity and pendant lights. And the backlighting and wall mount. Thank you! Can't add them to this project, but will save as ideas for future.

Flo, yes, that's the vanity (minus the white sink) and the toilet goes right next to it. We will cut the 24" slab in half and run a 12" backsplash above the sink and toilet. At only 4'x5', it's a really small space. But we could easy paint the vanity.

houssaon, I agree the vanity would look better centered, but the toilet goes beside it so no room to move.

Mama cita, I found the inspo picture here on Houzz and then found the agate at Cactus Stone & Tile (Phoenix, AZ) on clearance while I was shopping for something else. They had 24x24" mini slabs in about 8 different colors.

Thanks everyone for the guidance! I'll post updates, but will take a few weeks.

Thank you so much for the guidance! Went with SW Downing Slate and would do it again!