I have used BG Image Formatter before, but wanted a way to use responsive images. This module requires some developer setup, but can be used to do this.
This patch adds media module support to dev, but doesn't apply to the alpha1 release, so I'm using the dev version atm: https://www.drupal.org/project/responsive_background_image/issues/30675…
You probably want to set the background to no-repeat center center cover, but this isn't supported by the module yet: https://www.drupal.org/project/responsive_background_image/issues/30940…
Other background modules
https://www.drupal.org/project/bg_image_formatter
https://www.drupal.org/project/bg_img_field
https://www.drupal.org/project/ckeditor_bgimage
https://www.drupal.org/project/picture_background_formatter
https://www.drupal.org/project/simple_background_image_formatter
https://www.drupal.org/project/image_background_formatter
https://www.drupal.org/project/field_group_background_image
https://www.drupal.org/project/background_image