Find another piece of art work to go about the light switches.

Can you change out that cabinet over sink and put in a more modern one? That is really dating the room. If not then paint it. Red might be a good color :>)

It looks like you want to add red as your pop of color. Add a window treatment with a pattern, a small basket of hand towels.

Here is some inspiration.

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Roman Shade pattern inspiration

Deluxe Roman Shades Plain Fold, 25Wx96H Ikat Tiki · More Info

The bathroom is lovely, just needs a different colour for the walls. Which are drab. Get the colour wheel and pick the colour you like and then the colours either side of it or right over the other side and use them. Other than that cute little window, nice door and the sink and taps are great.

Go to HD or Lowes, they have all kinds of bathroom medicine cabinets. I'm sure you can at least get new door and if not, sure you can paint it. I would forget wallpaper, paint is much easier for this wall. If you don't use the cabinet I would just take it out and hang a new mirror over it. Get one with a red frame or a white one you can paint red.

Think about this. Start with your counter top. It is probably not going to change easily, so embrace it. Pick a color scheme from it such as the yellow or gold and use that for your accent. Painting the medicine cabinet and possibly the vanity doors to tie it all together

If you want wow, seems to me, you have to lose the white walls. Without knowledge of your style, this may be too much for you, but I'd paint the walls and window trim a deep charcoal that works with the color of the sink counter. The vanity base should be painted an off white that also works with the lightest tone in the counter top. The mirror suggested by Kimithy Nagel is perfect, drawing in more light and adding drama. I love something jumbo in a small space. The mirror should be a silver tone, as the faucet. Install one narrow floating shelf, about 6" deep, at the same height as the counter top. Run it from the counter top to the wall (over the toilet), caulk the joints, and paint it the wall color. A good place to put a few folded off-white hand towels, and cluster the small items that are now on the sink. A reverse roll solar shade on the window gives some privacy while letting the light and outside scenery in. No doubt, that would be wow. If you haven't tried deep toned walls before, this would be the place.

Just saw a bathroom with a collection of mirrors all different sizes and frames, it looked really good. Also a wire wine bottle holder which stored rolled up towels.