Ummm why do you want to put it on the side..... will be a hard task as whole idea of carpet is its removeable for cleaning, so would have to be loosely fitted. Which would mean snake will proberly be able to get behind it.
Some polystyrene backgrounds perhaps? You can make your own fairly cheaply. You could stick the reptile carpet there as insulation/security for the snake, but it might look better to have polystyrene 'rocks' and stuff going on.