Generally, you are allowed to hang things on the walls of your storage unit using appropriate methods that don't cause damage or leave permanent marks. Most storage facilities permit lightweight items such as paintings, posters, or mirrors to be hung using removable adhesive hooks or nails that won't create significant holes or damage the walls. However, it's essential to consult the specific guidelines of your chosen storage facility as some may have stricter rules regarding wall decorations. It's always wise to prioritize keeping the unit clean and undamaged so that you can retrieve your belongings in their original condition when needed.