No reason why you cannot, as long as you do not cover the condenser (black plate on back) or motor area. Condenser gets hot, so needs air to circulate around it to cool it, same with the compressor motor, needs air circulating to keep it cool. As for the rest, cover as much as you like, just remember, that you will need to get into it.
If auto defrost, make sure pipe from inside, bottom to back. is clear, and sits in the tray above your compressor motor in back, that allows water to drain away, and evaporate with heat from the motor, which also helps to keep the motor a bit cooler.
SD, October 2012