Oh, that's a cute picture! Please tell me that cute little guy (girl?) has a name.
Anyway, I don't like carefresh -- when it gets wet, it gets truly nasty. Pine is way, way out because of the phenols, and it WILL cause feed problems with the ball python. I've seen it over and over. Any loose substrate will get in the waterbowl and foul it, also, you have to feed in a separate container.
Aspen is safe. I use cypress mulch on my kingsnakes.
The rest get plain white paper towels. Prettier than newspaper, easy to clean, and cheap, cheap, cheap. You can wad them up under hideboxes to give them something to 'burrow' in. I just provide lots of hiding places for my snakes, and they seem to do fine.
Good luck, whatever you pick.
--Naamah