Detach images from posts in WordPress
Unattach is a very simple plugin which allows detaching images and other media from WordPress posts.
Download it from the WordPress site or simply search for “Unattach” from Plugins > Add New in your blog’s admin interface.
WordPress classifies all uploaded files (JPEG, PDF, MP3 etc.) as media. These media can be attached to a post, page or custom post type. However, as of WordPress 3.1, the only way to detach a media item from a post is to delete either the post or the media item.
This plugin adds a link below each media file in the Media Library admin view to allow users to unattach files.