I would begin by painting the dark wall to match the others. Keep it light and airy.

I agree about the dark wall. You have a very nice bathroom but the dark wall is very distracting.

Agree, no accent walls in a bathroom, especially when there is nothing to accent. Were you staying, a large piece of modern art would have been fun.

Is that an unfinished electric outlet by the tub? (the black hole.) I would have that finished before selling.

The first thing I notice in the pictures is the lack of any kind of towel holder. Perhaps a free standing holder between the tub and shower with some white fluffy towels would be nice. Something like this.

Agree! It’s a gorgeous bathroom but that black wall is jarring. Also close the toilet seat lol

You can keep the dark wall, BUT you have to put a large modern stencil on it using the color from the other walls! I assume you did this because you wanted some punch in the room, that will give you something to look at. Options: Floral (I see you have an orchid, you could do something with orchid flowers.., Peony, Rose, Magnolia, Gardenia, Poppies, Daisies, etc..), Geometric (anything you like), Earthy (Ferns, Stand of Pines or Deciduous Trees, a solitary Oak Tree w/ acorns, etc.) whatever, but make it a large print, not a dainty old-timey one, and it has to match the theme or feel of the rest of the house! I agree, finish your electrical finishes too. I suppose if you want to go cheap and easy and builder grade you will just put a large cheap picture on that wall... but you don't need a designer to tell you to do that!