Sure, you could use anything that would fit into the styrofoam chest as long as you can still put the top on!
I do use aluminum foil to line the bottom these days and that helps in two ways - I think it ups the heat inside the chest and wax that sometimes drips off of the paper towel can be easily peeled off of aluminum foil - more easily than off of the bottom of the styrofoam.
It's a bare bones wax melter - so there are bound to be individual improvements that will help it do even better.
Linda T