I can suggest you use paint, for example! You can paint the border a color that contrasts with the wall. This will create a visual break between the wall and ceiling. You can also use a stencil to create a decorative design. Crown Molding: Installing crown molding is a great way to add a decorative touch to your border. https://dundeedeco.com/product-category/wallpaper-borders/ There is a good selection of borders here.