Choosing a wallpaper can be tricky, but designer Eilla Adi knows a great place to start. “When thinking about wallcovering in a bathroom, I lean towards designs that are scalable,” says Adi.

On the other hand, designer Erika Bonnell notes, wallpaper may actually save money: “If you dress your walls boldly in wallpaper, it removes other things that need investment, like art. In the powder ...