Igor Benic

Multisite Featured Image changes the box of the featured image for all sites. It can be used also in a single instance of WordPress and not a MU installation.
This plugin changes the box in the way that the default pop-up is replaced with the classic Media Uploader where you can choose images. Images From URL do work.
For a greater Multisite experience you can combine this plugin with the <a href="https://wordpress.org/plugins/network-shared-media/" rel="ugc">Network Shared Media plugin</a> and have a complete Media Sharing site.
Read about it on this <a href="http://siderrz.com/wordpress-multisite-shared-featured-image/" rel="nofollow ugc">article</a>.
<h4>Features</h4>
<ul>
<li>Using WordPress Media Uploader to set Featured Image</li>
<li>You can set an image from URL</li>
<li>Images from URL will be downloaded into the WordPress Media and it can be used for anything else inside WordPress</li>
<li>Downloaded images are saved in every registered image size </li>
<li>You can set the Main site on which you will download the images in a MU installation</li>
</ul>

Multisite Featured Image

Multisite Featured Image changes the box of the featured image so that you can use the classic Media Uploader also with Network Shared Media.

wphigh

Admin Featured Thumbnail WordPress plugin can Add featured image thumbnail to WordPress admin columns. It will help you easy to know which post is attached the featured image. Add click the thumbnail will popup preview the full image.
It also support custom posts.
<a href="http://www.wphigh.com/portfolio/admin-featured-thumbnail-wordpress-plugin" rel="nofollow ugc">Feedback Admin Featured Thumbnail</a>

Admin Featured Thumbnail

Add post thumbnails to admin list of posts.

Multisite Featured Image vs Admin Featured Thumbnail