Frank P. Walentynowicz

Setting featured images for posts / pages could be very time 
consuming, especially when your media library holds hundreds of 
pictures. Very often we select the same thumbnail for posts in 
particular category. This plugin automates the process by inserting a 
thumbnail based on category / thumbnail mapping while post / page is 
being created or updated. Now bundled with FPW Post Thumbnails.

FPW Category Thumbnails

Assigns a thumbnail based on categoryid/thumbnail mapping to a post / page when the post is created or updated. Built-in FPW Post Thumbnails.

Kyle Gilman

<h4>A plugin to make video players, thumbnails, multiple resolutions, and video galleries.</h4>
This video plugin adds several options to any video uploaded to the WordPress Media Library. If your video can be played natively in your browser, or if you have FFMPEG installed on your server (optional), you can generate thumbnails from your video. Using either the “Generate” or “Randomize” buttons will create a selection to choose from. Click “Insert into Post” and you’ll get a shortcode in the post editor that will make a flexible, responsive video player.
If you provide multiple H.264 resolutions, Videopack can automatically select the one closest to the size of the player or a resolution of your choice, and provide a button for users to select the resolution manually. If FFMPEG is installed on your server, Videopack can encode the videos automatically.
You can also use Videopack to create a popup video gallery. The shortcode uses options similar to the <a href="https://codex.wordpress.org/Gallery_Shortcode" rel="nofollow ugc">WordPress image gallery shortcode</a>. In its simplest form it will create a gallery of all videos attached to the post.
You can now add advertisements to your videos using the <a href="https://www.videopack.video/add-ons/videopack-ads/" rel="nofollow ugc">Videopack Ads</a> premium add-on which you can purchase from the Add-ons tab of the Videopack Settings page or on the <a href="https://www.videopack.video/add-ons/videopack-ads/" rel="nofollow ugc">Videopack website</a>.
Not compatible with the Block Editor. Please continue to use the <a href="https://wordpress.org/plugins/classic-editor/" rel="ugc">Classic Editor</a>.
Visit the <a href="https://www.videopack.video/docs/" rel="nofollow ugc">Videopack Documentation pages</a> for more info.

Videopack

Great solution for generating thumbnails from images. 
Thank you for the work put into this plugin.

Excellent

Makes video thumbnails, allows resolution switching, and embeds responsive self-hosted videos and galleries.

FPW Category Thumbnails vs Videopack