I am no carpet python expert, but Animal Plastics makes a cage that is designed specifically for carpets. http://www.animalplastics.com/ Click on "specialty cages" on the left and then choose "the carpet cage" and you'll see a picture of it. But basically its a horizontal cage with a shelf.
AP offers belly heat (flexwatt), but personally, I would opt to use an RHP for carpets due to their semi arboreal nature. Reptile Basics offers a quality RHP - http://www.reptilebasics.com/rbi-radiant-heat-panels
Another great place is pvccages.com. Jim offers some great options for carpets and provides some details and help to choose the most appropriate cage - http://www.pvccages.com/new/?page_id=233
If I were getting a carpet python, I would get one from pvccages. My gtp's cage came from there and I'm very happy with it. And you can get one from Jim that is complete with perches, light, and RHP - just get a t-stat and plug and play, lol.
Incidentally, horizontal cages are generally preferred even for most arboreal snakes - carpets and gtps included - as it is easier for them to thermoregulate side to side rather than up and down.![]()