Add wallpaper or paint via wall finish material
Give a wall a wallpaper or paint finish by choosing it from the wall's finish material options.
To add wallpaper to a wall, select the wall and open the first option, finish material, on the left panel. Go to the material/house button, choose wall texture, then wallpaper, and select an option.
To apply paint, select the wall, open finish material, go to wall texture, and choose from solid paints or texture paint.