On wall opposite vanity, with door closed:

(Honestly -- worst photo uploader EVER.)

Lastly, the flooring:

I lied -- THIS is the last pic ... Lighting fixture is oil-rubbed bronze with textured alabaster shades.

Ida - im feeling ambitious and thinking desert sunset. Ombre terra cotta with the darkest shade at the bottom and lightest at the top. Then a pale twilight color on the ceiling. Working around the pumbing would be a bit of a pain but if you use one color and simply add white it shouldnt be too difficult. Martha Stewart has a video. Is this too 80'shall retro for you?

lissam, I love that! Actually, desert sunset is exactly what I envision when I think of this little room, always calling to mind one of the most spectacular skies I ever saw when I was camping out in Arizona a number of years back. Streaks of purples and oranges that faded into pink. Stunning. I don't think I would trust myself to even know how to begin to paint an ombre technique, even with a tutorial though. Hmmm ... I wonder if there's wallpaper that mimics such a thing.

ETA: Holy cats -- it IS a thing!

https://www.architecturaldigest.com/story/ombre-wallpaper-trend

Here's a couple of pretty peel and stick options (bottom one is probably too bright tho). I wonder what the learning curve is on putting this stuff on walls.

Just read it is not intended for textured walls though, so not sure if it would work. These are polyester fabric panels that go up in a certain order.

Then there's purple grasscloth wallpaper. Yummy.

This one's interesting too.

Rough paint mockups:

I love the idea of a sunset inspiring the wall colour here. Those purples and oranges are fab. You wouldn't happen to have any sheets of those colours, would you? That would be an "easy" way to test a darker colour in that small space. Your art is gorgeous, btw. (But you know that already. ;-))

Thank you, tartan! I don't have any such sheets in those colors, unfortunately -- but am sitting here like I have nothing better to do this afternoon mocking up pathetic colored walls in the Paint app. ;-) I'm actually kinda liking the deep brown, which I certainly did not expect to. it's a far cry from the sunset colors, but I think it might really set the art off nicely. Hmmmm ...

The brown is the only color that does not set off the art for me. The ombrés, purple grasscloth, teal and coral do though and look good with your vanity. I wish I had someplace for the ombré!

No to the brown, eh? Maybe I'm liking it because it seems the most dramatic. ;-)

Deeper terra cotta:

Uh, no, I LOVE the brown!

Ida, can you try something like this as a mock up?

The brown looks good, but I really like the deeper terra cotta. Since you say all your walls are presently the same color, we know that the walls outside your PR are not powder blue. :)

Bonnie, here's a duskier purple.

Dusky purple gets my vote.

I REALLY like the idea of an eggplant-y purple....

Wow, the photos just quadrupled in size for me.

Here's another view of the deep terra cotta. It's ALMOST brown, but not quite. (I'm sure DH will say this looks like poop. Hmmmph.)

And another dusky purple ...

What about purple with gold grasscloth on the ceiling? It seems sunsety to me...

Ooooh, Penny! Now THAT's an idea ...

I like the dusky purple and grass cloth on the ceiling is a brilliant idea (I trust your cats can’t walk upside down!)

Just coming back to say a big THANK YOU to all who made such helpful, excellent suggestions. I'm still mulling this over, not even completely sold on changing the walls. I do wonder if having one tiny room in the house that has different colored walls will be something I'll end up regretting. And painting or papering this little space will require some effort, as the vanity will need to be moved, which will entail disconnecting plumbing. On the other hand, I do love the look of a special powder room, and can completely understand the desire one has to create such a thing! Many of you know me, and my tendency to jump right in and tackle a project once I start formulating an idea ... I think I'll give it some more time to germinate though. Anyway, thanks again for all of the input. Greatly appreciated!

Jen, I would consider Sherwin Williams River Rouge. It is a plum like color with almost cocoa undertones. I have it in my small master bath and it works very nicely with southwest type colors. I unfortunately do not have a picture, but I found this dining room done in the same color. Dining room painted in river rouge by Sherwin Williams.

Ooo, that's a nice colour, tishtoshnm!

IdaClaire, sometimes, it's fun to just ponder these projects. :) You're lucky to have those mock-up skills to help you visualize your colour ideas.

Tishtosh, that's absolutely gorgeous! Thanks for sharing the paint name. I can absolutely visualize that with the typical SW colors, and know your bathroom must be stunning! Did you paint your ceiling in that color as well, or is it lighter?

The ceiling is a light, sky blue. I don't remember what shade right now. Dh is not a fan of painting the ceiling the same color but maybe someday.

I haven't tried River Rouge yet, but I will. Here is the room in SW Carnelian. (The SW site won't let me paint the entire picture for some reason, but this at least gives an idea of how the color would look.)

OK, River Rouge. Sorry the toilet got painted too. I do like this color a great deal.

I am hoping that I can get this posted, maybe this time will be it! The carnelian above also looks lovely.

That's gorgeous, tishtosh! I love it with the ceiling painted blue! I think River Rouge might be quite nice with our vanity top, as the brown marble seems to have a bit of a purplish cast to it.

SW Cordovan:

I love that orange, Annie! I'd be coming out of there smiling so big. :D What a happy colour.

Oh, that is fabulous, Annie! Definitely a jolt of happiness on those walls! I love it, but then again, I'm an "orange" girl and adore the color in all forms.

Are walls in adjacent rooms also painted in other colors, or do you have the same paint throughout in the rest of your home? I keep wondering how it will look to have just that one tiny room in our house painted a different color. It's right off the hallways extending from the foyer before you enter the open living/kitchen/dining area. Not that its location really matters, but I'm trying to wrap my head around how it would look to have a brilliantly-hued little "cave" behind that one door.

For me, having a "brilliantly-hued little cave" in a sea of neutral would be lovely and unexpected...

And you can paper the ceiling yourself, absolutely...

I'm not a fan of a feature wall in a powder room...it's such a small space with so many things going on already. But that's just my own preference, of course.