Palasthotel

greatestview

This plugin redirects attachment pages to the post, where they are placed (via 301). If there is no parent page, it redirects back to the WordPress home URL (via 302).
Further, when editing a post, the option to link images to their attachment page is hidden via CSS (except it is selected by default).

Disable Attachment Pages

Redirects attachment pages to the post, where they are placed, and hides backend option to link images to attachment page (if not default).

MMDeveloper

A wordpress plugin that allows you to add categories to attachments. Similar to https://wordpress.org/plugins/map-categories-to-pages/, but just allows you to set the attachment’s category.
Map Categories to Attachment displays the category box on the “Edit Attachment” page. By default, Every attachment in wordpress is mapped to the default category but this plugin gives the option to select categories for an attachment.
Built by The Marketing Mix Perth: http://www.marketingmix.com.au

Disable Attachment Pages vs Map Categories To Attachment