tantive

This plugin allows background images to be set for all blocks. 
You can set CSS background-image, background-repeat, background-attachment, background-position-x, background-position-y, and background-size.

Tantive Set Background

Example block scaffolded with Create Block tool.

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.

Tantive Set Background vs Background Per Page