Stephen Mekosh

Ordered Thumbnails is a WordPress plugin that allows you to display thumbnails based on images that have been attached to a post. This plugin also allows you to specify which thumbnail appears next to a post with multiple images by ordering the thumbnails in the Gallery tab of the WordPress “Add Images” lightbox and placing the thumbnail desired in the first position.
To style how the thumbnail appears on your page, you may pass optional CSS class names to the plugin, which will then be applied to the <code><img></code> tag returned. Alternately, by setting the display parameter to “false”, Ordered Thumbnails will return the thumbnail URL, height, and width as a PHP array to be used however you see fit. If no images have been attached to a post, the plugin fails gracefully and returns “false”. This plugin will work anywhere the WordPress posts loop is used and works particularly nice in combination with <code>the_excerpt</code> for archive pages.

Ordered Thumbnails

Display a thumbnail based on post images with no additional uploads. For multiple image posts, thumbnail respects Gallery sort order.

ryanpcmcquen

Makes local copies of all the linked images and pdfs in a post, adding them as gallery attachments.
Source & support:
https://github.com/ryanpcmcquen/import-external-attachments
<h4>Credits</h4>
This plugin is based on the work done in the “Import External Images” plugin by MartyThornley.
https://github.com/MartyThornley
HTTPS support added by IvanDoomer: 
https://github.com/IvanDoomer
PDF support added by bengreeley: 
https://github.com/bengreeley
Most of the JavaScript was rewritten from the original plugin, to reduce the 
number of global variables.

Import external attachments

Makes local copies of all the linked images and pdfs in a post, adding them as gallery attachments.

Ordered Thumbnails vs Import external attachments