glowrocks

For posts and pages with no featured image, and no images associated with the entry, a random image is selected from the media library and set as the featured image.
The plugin currently does not test for images associated with the entry.
Instead, install and run the Easy Add Thumbnail plugin (https://wordpress.org/plugins/easy-add-thumbnail/).
That plugin will set the featured image on all entries that both have no featured image AND have an image associated with the post.
What is left is entries without featured images and without any images.
This plugin provides a random image from the sites media library so that index pages look more interesting (and possibly confusing/humorous depending on which image is randomly selected.)
There is a notice at the bottom of each post the plugin has updated noting the random image. In a future release, this note will be optional via the standard user interface, but for now one has to edit the plugin and remove the last “filter” line. This notice is not displayed if the plugin is removed.

Random Auto Featured Image

For posts/pages with no featured image, & no images associated with the entry, a random image is selected from media library & set as featured image.

blogvii

B7 Random Images allows you to display a selection of random images from your media library on any post or page using a simple shortcode. You can easily choose the images you want to display by specifying their media IDs, the total number of images to show, and the size of the images.
<h3>Parameters</h3>
<ul>
<li>media_ids: (string) A comma-separated list of media attachment IDs (required).</li>
<li>total: (integer) The number of random images to display (default: 1, max: 5).</li>
<li>size: (string) The size of the images (default: ‘full’). Options include ‘thumbnail’, ‘medium’, ‘large’, ‘full’.</li>
</ul>
<h3>How to use and examples</h3>
To use the B7 Random Images plugin, follow these simple steps:
<ol>
<li>Insert the Shortcode: Add the shortcode to your post or page where you want the random images to appear. The basic format is:</li>
</ol>
<ul>
<li>media_ids: Replace <code>"1,2,3,4,5"</code> with the actual IDs of the images you want to display, separated by commas.</li>
<li>total: Specify the number of random images to show (between 1 and 5). For example, <code>total="3"</code> will display 3 random images.</li>
<li>size: Choose the size of the images. Options include <code>thumbnail</code>, <code>medium</code>, <code>large</code>, or <code>full</code>. The default is <code>full</code>.</li>
</ul>
<ol>
<li>Example Usage: Here are a few examples of how to use the shortcode:</li>
</ol>
<ul>
<li>
To display 2 random images from specific media IDs in full size: 
 <code>[blogvii_random_images media_ids="10,20,30" total="2" size="full"]</code>
</li>
<li>
To display 5 random images in medium size: 
 <code>[blogvii_random_images media_ids="5,15,25,35,45" total="5" size="medium"]</code>
</li>
</ul>
<ol>
<li>View the Results: After adding the shortcode, preview or publish your post/page to see the random images displayed.</li>
</ol>

B7 Random Images

Display random images from your media library on any post or page using a simple shortcode.

Random Auto Featured Image vs B7 Random Images