This is a simple WordPress plugin that allows control over the display of background images.
It will switch on custom background support for those themes that don't have it and then allow background images to:
- be displayed on home page only
- use a post's featured image (if the theme supports post_thumbnail)
- use a category's featured image (if the WPCustom Category Image is installed)
More about this plugin at https://premium.wpmudev.org/blog/how-to-properly-add-background-images-to-your-wordpress-site