Anil Sardemann

This plugin distinguishes between block and non block themes to add a fullscreen background image to WordPress. It is set either to the body tag (in case of a non block theme) or to the wp-site-blocks class (in case of a block theme). Upload an image or choose one from your media library. Simple plugin that allows you to set a background image for your website easily.
<a href="https://playground.wordpress.net/?plugin=custom-background-image" title="WordPress Playground Demo" rel="nofollow ugc">Demo</a>

Custom Background Image

Simple plugin that allows you to set a background image easily. Upload an image or choose one from your media library.

Andy Charrington

Easily add background options on a per page/post basis.
Currently the plugin includes the following features-
<ul>
<li>Add a background image</li>
<li>Options for vertical & horizontal repeating</li>
<li>Fade out the bottom edge of your background image</li>
<li>Choose background colour</li>
<li>Child pages of a page with a custom background will inherit the parent page background settings.</li>
</ul>

Background Per Page

Background Per Page allows you to set a custom background per page (or post) as well as set up a default background for all other pages/posts.

Custom Background Image vs Background Per Page