This is my version of the layout_builder_backgrounds module on drupal.org (https://www.drupal.org/project/layout_builder_backgrounds). All credits to the original author. I have made modification to the storage to ensure settings are saved in the third party setings of the section instead of in the lay-out.
It is currently depnding on 2 Drupal core patches:
- https://www.drupal.org/project/drupal/issues/3101655
- https://www.drupal.org/project/drupal/issues/3044117
And can be easily exstended to section content (blocks) once the following patch is in.