How can I further enhance the beauty of my newly renovated downstairs bathroom by updating the light fixture and switch cover?

I think you should probably start by focusing on the window and the wallpaper. Maybe consider smoothing out the wall where the window is located to cover up that pipe. You can then use the space created for storage of bathroom items like toilet paper and toothpaste. It would be helpful to see a better picture of the entire room to give a more accurate suggestion. It’s tough with such a small space, but that’s my initial thought.