redwerks

This plugin allows posts and pages to have individual custom backgrounds. A full-body background that shows up on the post page itself can be specified. As well as background that just covers the content area and shows up on all places the post is visible.

Post Backgrounds

Allows posts and pages to have individual custom backgrounds. Both as body backgrounds and as content backgrounds.

markoarula

With this plugin you can enable your users to switch website between Night Mode and normal style smoothly to improve the readability of text, images and videos.
Reading website content at night time can be difficult. Help your visitors read more articles, spend more time on your website and protect their eyes from being hurt.

WP Night Mode

Allow users to change the website style while reading at night, enabling them to easily read and spend more time on your site.

Post Backgrounds vs WP Night Mode