offseo

<p>This plugin add to any page the images from the public flickr’s tag feed.<br />
You must use a shortcode like this:<br />
[myflickrtag tag=”tag”]<br />
You can configure the tag your need to use.</p>
<p>We use a third party service from https://flickr.com to display the image from the public feed’s tag. You can read the features of this feed here https://www.flickr.com/services/feeds/docs/photos_public/</p>
<p>You can read the Flickr privacy Police https://www.flickr.com/help/privacy/</p>
<h3>Contribute</h3>
<ul>
<li>
<p>Active development of this plugin is handled <a href="https://bitbucket.org/offseo/flickrtag/src/master/" rel="nofollow ugc">on Bitbucket</a>.</p>
</li>
<li>
<p>If you want to help us translate this plugin you can do so <a href="https://translate.wordpress.org/projects/wp-plugins/my-flickr-tag/" rel="nofollow ugc">on WordPress Translate</a>.</p>
</li>
</ul>
<h3>Credits</h3>
<ul>
<li>Author: <a href="https://offseo.com/" rel="nofollow ugc">Brad Branson</a></li>
</ul>
<h3>Requirements</h3>
<ul>
<li>PHP 5.2.4 or greater</li>
<li>WordPress 3.9 or greater</li>
</ul>
<h3>Settings</h3>
<p>After you have activated <em>My Flickr tag</em> you must to add the shortcode to any page or post.<br />
The plugin will display a custom window inside that page or post with your configuration<br />
[myflickrtag tag=”dish”]<br />
tag: the tag of the images you want to show.</p>


My flickr tag

jmarreros

<p>This Plugin allows to use an external image as Featured Image, this can be especially useful if you house your images in another location.</p>
<p>This Plugin is compatible with Nelio External Featured Image Metadata, so you can reuse your data in case you want to uninstall Nelio Plugin.</p>


External URL Featured Image

It is what I was looking for: simplicity.

$external_image = get_post_meta( $post->ID, '_dcms_eufi_img', true );

Works well for me

Use an external url image as Featured Image for your posts, pages, and other kind of post types.

My flickr tag vs External URL Featured Image