Jess

Thumbnail Updater does exactly what it’s name implies: it updates thumbnails. WordPress 2.9 introduced support for 
post thumbnails but one problem is that the support is not backwards compatible—meaning that if you downloaded or created 
a theme that supports post thumbnails, any images uploaded prior to the activation of that theme will not have the new thumbnail size.

Thumbnail Updater

A plugin for updating your thumbnails whenever a new thumbnail size is added with add_image_size()

Jean-David Daviet

Download Media allows you to directly download medias from the media library to your device in one click.
You can download medias one by one, or in bulk.
<h4>Need Help? Found A Bug? Want To Contribute Code?</h4>
Support for this plugin is provided via the <a href="https://wordpress.org/support/plugin/download-media" rel="ugc">WordPress.org forums</a>.
The source code for this plugin is available on <a href="https://github.com/JeanDavidDaviet/download-media" rel="nofollow ugc">GitHub</a>.
<h3>List of hook available</h3>
Filters
<ul>
<li>download_media_settings_cap – Set default capability for plugin’s settings modifications</li>
<li>download_media_output_dir – Set default output directory for plugin’s zip files</li>
<li>download_media_cron_intervals – Allow the modification of the plugin’s cron intervals</li>
<li>download_media_cron_daily_second – Allow the modification of the daily cron interval of time</li>
<li>download_media_cron_weekly_second – Allow the modification of the weekly cron interval of time</li>
<li>download_media_cron_montly_second – Allow the modification of the monthly cron interval of time</li>
<li>download_media_zip_directory – Set default zip files directory location</li>
</ul>

Download Media

Allows medias in the media library to be direclty download one by one or in bulk.

Thumbnail Updater vs Download Media