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  …

fahrirusliyadi

WordPress generates thumbnails in the same directory with the original image. This plugin change this behavior by generating the thumbnails in a separate directory. The thumbnails will only be generated when they are needed and has not been generated.
This plugin will only move the thumbnails location for new uploaded images. To move all thumbnails, you need to delete all existing thumbnails (see FAQ).

Fr Thumbnails Folder

Move thumbnails file location to {$upload_path}/thumbnails or {$upload_path}/sites/{$blog_id}/thumbnails for multisite.

Admin Thumbnails vs Fr Thumbnails Folder