You can add any number of image planes to a camera.
You use image planes as visual references while building a model or as a means of compositing background or foreground images during rendering.
To add an image plane to a camera using Import Image Plane
The image plane appears in the modeling window.
To add an image plane to a camera using the Camera Editor
The image plane appears in the modeling window, and an image plane swatch appears in the Image Planes section of the Camera Editor.
To delete one image plane from a camera
The image plane is deleted from the camera’s window, and from the image plane swatch list in the Image Planes section of the Camera Editor.
To delete all image planes from a camera
All image planes are deleted from the active window.
To delete all image planes from all cameras
All image planes are deleted.