Sergey Biryukov

Allows to find all posts where a particular attachment (image, video, etc.) is used.
Adds a “Used In” column to the list view in Media Library, as well as to the attachment details modal.
Finds posts that use the image (including any of its intermediate sizes) in post content, or as a featured image. Works with custom post types too.
Inspired by a <a href="http://wptavern.com/the-problem-with-image-attachments-in-wordpress" rel="nofollow ugc">WP Tavern post</a> on image attachments.

Find Posts Using Attachment

Allows to find all posts where a particular attachment is used.

shawfactor

This plugin allows you to create duplicate images in the media library, rather than having to create a new copy of the image and upload it to WordPress again.
It works by copying the post and its metadata into a totally new file in the media manager. Any changes you make to the new copy of the attachment — updating the caption or cropping, for example, will only be applied to the new attachment, not to the original.
This is useful if you want to edit or crop an existing image without effecting the original
To use, go to the Library tab and you will see a copy file link below each media (this will only appear in list view, see faq)

LH Copy Media File

Thanks! It does what it's supposed to do.

Great plugin! Does what it's supposed to.

Allows you to create duplicate images in the media library.

Find Posts Using Attachment vs LH Copy Media File