If they can fit, they eventually will. They love tight spaces where they feel secure and safe from predators.
Although those backgrounds look nice, they're not very practical. I'll think you'll find that most experienced keepers don't use them. They're more of a pain than the benefit of aesthetics is worth.
Well, I mainly got them to make him feel a bit more safe & secure but maybe I can just wrap the outside with something else. Gonna finish plugging that hole and see how he does for a bit.