I'm guessing you want something that looks nice for a hide.. you can look at the pet store and try to find something with one entryway, that is otherwise completely enclosed. The half logs are too open to be very secure for a ball python. A lot of people use the plastic plant saucers that are made to go under potted plants to catch the water. You can easily cut or melt an entry hole either in the top or the side of these, and they're great hides.

A 20 gallon really is big for a young ball.. if you really really want to use it, you have to have lots of hides. Open spaces are scary for baby BPs, so multiple hides are a must if you want the snake to eat.

Drift wood is fine decoration. You may want to bake it for about 20 minutes in the oven to make sure and hitch hiking bugs on it are dead.