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.

N Atta Kusi Adusei

GrottoPress

IMPORTANT: This plugin requires PHP version 5.3 or newer. We recommend PHP version 7.0 or newer.
Smart Featured Image is a WordPress plugin to automagically add featured images to posts using images inserted into post content, if no featured image is added to a post.
WordPress, by default, requires you to explicitly set a featured image for each post even if there are images already used in the post.
The Smart Featured Image plugin frees you from the extra step of setting a featured image by saving the first local image it finds in the post content as featured image.
The plugin displays a configurable default image if no image is found in post content.
The default image settings are available via the Media Settings screen (‘Settings‘ -> ‘Media‘) in the WordPress administration area. There are options to set the default featured image for each public post type.
Smart Featured Image works by:
<ol>
<li>Checking if a featured image was added to the post.</li>
<li>If no featured image was added, the plugin looks for images attached to the post (ie images uploaded to the current post). If found, the first attached image is saved as the post’s featured image.</li>
<li>If no image was attached to the post, the plugin looks for an image inserted into the post content, but not necessary attached to the post. If found, the first local image inserted is saved as featured image.</li>
<li>If all of the above fail, the plugin falls back to the default featured image set for the post type in question under the Default Featured Image section of the Media Settings screen.</li>
</ol>
You would notice that, in step 4 above, the plugin does not save the default featured image as the featured image. Rather, it simply returns that image whenever a call to get the post thumbnail is made. This is the intended behaviour.
This means, any time the default featured image changes, all posts that used the previous default featured image would automatically use the new default featured image since the old one was never saved to the database as featured image.
You can disable smart featured image for any specific post by setting a <code>no_sfi</code> custom field to any value other than <code>0</code>. Delete the custom field, or set to <code>0</code>, to restore plugin functionality for that post.
Give Smart Featured Image a shot. You will love it.

Smart Featured Image

Automagically add featured image to posts using images inserted into post content, if no featured image is explicitly added to post.

Multisite Featured Image vs Smart Featured Image