John Godley

Enhances the WordPress media library by allowing you to rename the underlying media files. Any change to a media item’s title will result in the media filename also being changed.
See the screenshot for more details of where to rename media files.
Note that all thumbnails will also be renamed. If you are using a caching plugin, such as WP Super Cache, then you will need to clear your cache so that any references are updated. This plugin does not update existing direct links to files (links inside a WordPress gallery will change).

Rename Media

Rename underlying media files from the WordPress media management interface

neoslab

Medias Toolbox allow you to sanitize and rename automatically media files during upload using severals predefined patterns. Furthermore Medias Toolbox offer you the option to compress your JPG and PNG image file to optimize your website and page loading time.
<h3>License</h3>
Good news, this plugin is free for everyone! Since it’s released under the GPL, you can use it free of charge on your personal or commercial site.

Medias ToolBox

Do what the title say

Medias Toolbox allow you to sanitize and rename automatically media files during upload.

Rename Media vs Medias ToolBox