barteled

Slideshow background adds a full size, smooth transition slideshow to the background of a WordPress site. Images can be selected from the media library or uploaded via drag-and-drop. Every page load will begin at a random position in the image loop so that users are not presented with the same start image every page change.
Additionally, the images maintain their aspects ratios during resize and turn off for mobile users.
This plug-in was conjured up by a nerd at <a href="http://think-bowl.com/" title="It's less of a tank and more of a bowl." rel="nofollow ugc">Think Bowl</a>

Simple Slideshow Background

Display a full size slideshow in the background featuring images from the media library.

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.

Simple Slideshow Background vs WP Night Mode