Enrico Sorcinelli

Feature Image Extended extends featured image functionality allowing:
<ul>
<li>Hiding featured image in your themes for all post types.</li>
<li>Adding link to the featured image.</li>
<li>Adding thumbnail featured image in administration screens listing.</li>
<li>Featured image quick-editing.</li>
</ul>
<h3>Usage</h3>
Once the plugin is installed you can control settings in the following ways:
<ul>
<li>Programmatically by using <code>featured_image_extended_settings</code> filter (see below).</li>
<li>Using the Settings->Featured Image Extended administration screen.</li>
</ul>
If your theme uses a different call other than <code>the_post_thumbnail()</code>/<code>get_the_post_thumbnail()</code> in order to get the featured image, this plugin might not work. 
So, in order to get extended featured image settings and apply to your pages, you should use <code>featured_image_extended()</code> (see below).
<h3>API</h3>
<code>featured_image_extended( integer $post_id = null )</code>
It returns an array containing featured image extended information of <code>$post_id</code> post (or current post if you don’t supply an argument) like following:
<pre><code>array(
 'show' => true,
 'url' => 'https://myurl.com',
 'target' => '_blank',
 'title' => 'Image title',
)
</code></pre>
<h4>Hooks</h4>
<code>featured_image_extended_settings</code>
Filter plugin settings values.
<pre><code>apply_filters( 'featured_image_extended_settings', array $settings )
</code></pre>
<code>featured_image_extended_admin_settings</code>
Filter allowing to display or not the plugin settings page in the administration.
<pre><code>apply_filters( 'featured_image_extended_admin_settings', boolean $display )
</code></pre>

Featured Image Extended

Feature Image Extended extends featured image builtin functionality.

GLS Inc.

This plugin adds featured images (thumbnails) to the default WordPress RSS feed. 
WordPressのデフォルトのRSSフィードにアイキャッチ画像(サムネイル)を追加するプラグインです。
Once activated, featured images will be automatically added to the RSS feed. 
プラグインを有効化すると、自動的にRSSフィードにアイキャッチ画像が追加されます。
This plugin is provided as-is, without any guarantees of functionality or support. 
本プラグインは無償で提供されており、動作の保証やサポートはありません。
Standard RSS Feed URLs: 
– Post Feed: <code>[your-site]/feed/</code> 
– Category Feed: <code>[your-site]/category/category-name/feed/</code> 
– Custom Post Type Feed (example): <code>[your-site]/feed/?post_type=custom-post-type</code>

GLS RSS Thumbnails

Adds featured images to WordPress RSS feeds. / WordPressのRSSフィードにアイキャッチ画像を追加します。

Featured Image Extended vs GLS RSS Thumbnails