Views menu > Update Background Image (available only when a viewport background is displayed)
This command updates the background image displayed in the active viewport. If the active viewport is not displaying a background image, this command is unavailable.
Use this command to update the background for changes that are not updated automatically, such as the following:
Reassigning the map, or changing any parameters affecting the map in the Viewport Background dialog.
Changing the aspect ratio.
The following changes update the viewport background image automatically:
Changing the camera view.
Undo (for views).
Undo (for objects).
Assigning a different view type.
Procedure
To update the background image displayed in a viewport:
Activate a viewport that contains a background image.
Choose Views menu > Update Background Image.