The panarama, image, and box backgrounds only render for the ACTIVE camera. In order to have another camera see the background, you must make the unwanted camera-active variable "0", and the camera_you_want-active variable "1".
So it would be like: (the dashes indicate where the data point is)
camera00
_
active| | | | | | | | | |-| | | | | | | | | |
camera01
_
active| | | | | | | | | |-| | | | | | | | | |
the first frame is defaulted, camera00 will automatically be active, camera01 will not.
in the 10th frame, the camera00 will have be deactivated with the value of 0, while camera01 will be activated with a value of 1. This is really useful if you have a camera set up with a parent object so it acts like a hoodcam or a cockpit view. By the way, I believe the active variable doesn't show up on the timeline by default, so you may have to double click the name of the camera and look under the "other animatable properties" to use it the first time with that camera, then it will show up on the timeline. Good luck!
