Coming in late. I’d add a new chair rail just above the toilet or aligning with the window sill. I’d leave the slanted wall a light color. I like the dark green wainscoting that I like both the wall paper patterns and have cushions with the first William Morris design. I think powder rooms are the perfect place to do something that is a little over the top. In our old house I used stuff that was leftover from jobs that an interior designer I was working with had. We had a toile wallpaper that I would never want to live with in large quantities and pinkish marble on the floor. If that sink had been on the market yet it would have been perfect for our space, but we ended up with something almost as small.
Our wallpaper was something like this:
