If no specialized cardboard storage boxes can easily be purchased in the area, there is always the option of protectively wrapping the mirror or wall decoration. This can be done with bubble wrap or even thick blankets. Packing tape or clear plastic wrap can be used to securely hold the blanket or bubble wrap around the mirror or wall decoration. It is important that the corners of the mirrors or pointy areas of the wall decorations be covered with cardboard fittings during the move and the time that they are in storage. Not only does this help protect these weak parts of the items, but it also prevents the points from hurting the people that carry them or gouging holes in the cardboard box, blanket, or bubble wrap and causing the wall decoration to fall out and break.
These items should never be stored flat or precariously balanced on top of other stored things. Oddly large mirrors and framed artwork can actually collapse from their own weight if they are stored flat. They should also not be leaned directly against the hard wall because they could break if they are bumped into. In addition, they should not be sitting directly on the floor where they might accidentally get kicked. For the best protection, the mirrors and other large wall decorations should be layered between mattresses that are raised up from the storage unit floor by pallets.
Photo Credit: painting.about.com