I agree with babybluetx23, Duce loves to sleep on a cold surface. In the winter he will lay on his blankets/towels during the night. In the day, he will push them to one side and just lay on the plastic liner.
He also likes to dig at the liner to let us know he is ready to get out of bed. . . . :p At this time I make him wait until I am ready to let him out. Its funny, he will lay on the kitchen tile them get up an lay next to the heater. Funny dog. My advice go to Goodwill and get towels and blankets. This way you don't care if they wreck their crate liners. (Duce also has a habit of chewing on the corners of the towels.)
Good luck