mbecher

If your theme supports the thumbnail feature introduced in WordPress 2.9, this plugin will display attached thumbnails on the admin area’s manage posts and manage pages screen, similar to the media management page.

Admin Thumbnails

If your theme supports Wordpress 2.9's thumbnail feature, this plugin displays thumbnails on the admin area's manage posts and manage pages  …

Alex Mills

By default, WordPress uses the center of an image when creating cropped thumbnails. SmartCrop attempts to find and use the most interesting part of an image and centers the cropping on that portion of the image.
This process is entirely automatic and cannot be manually controlled. There are other plugins out there if you wish to manually specify where you want thumbnails to be cropped.
Since this analysis process can be slow on large images, thumbnails are initially center cropped and later asynchronously regenerated to be smartly cropped. This avoids the uploading of new images from being slow. The one side effect of this however is that your browser may load and cache the centered thumbnail before it’s re-cropped.
Want to smartly crop your past image uploads? You can use my <a href="https://wordpress.org/plugins/regenerate-thumbnails/" rel="ugc">Regenerate Thumbnails</a> plugin to trigger that. Make sure to uncheck skipping existing thumbnails.
<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/smartcrop" rel="ugc">WordPress.org forums</a>.
The source code for this plugin is available on <a href="https://github.com/Viper007Bond/smartcrop" rel="nofollow ugc">GitHub</a>.

SmartCrop

Instead of cropping to the center of an image, SmartCrop attempts to use the most interesting part of the image for the thumbnail.

Admin Thumbnails vs SmartCrop