The Add-on attempts to import an image for every camera that is selected when the "Add Backgrounds" button is clicked.
The Add-on leaves the names of cameras and image files intact when the dynamic renaming functions are used.

When "Cam Math" is enabled the labels for the Add Prefix/ Suffix buttons and the Remove Prefix/ Suffix buttons turns red to indicate that these field have become mandatory to use, if your camera name uses anything other than numbers. Math functions can't be applied to the camera name if it contains text.

The Add-on contains a small instructional pop up for providing a quick refresher of the functions.

Installation:

Install Batch Background Importer into Blender by going to edit>preferences>add-ons.

Click the install button to bring up the file browser window and select the "Batch_Background_Importer.zip" file from the location it is stored on your computer. Once the add-on is selected, click the "Install Add-on" button.

Enable the add-on by clicking the check box on the Batch Background Importer panel that is now in your list of add-ons.

Once installed the Batch Background Importer panel will appear the camera properties tab in the properties window. The add-on also includes drop down with instructions.