Comments of Posts, Pages or Image Attachments can be controlled via WordPress core feature.
Following articles will be helpful to you.
1. Make sure “Discussion” is checked in the Screen Options of a Post, Page or Attachment
2. When the “Discussion” will be checked you will find “Allow Comments” and “Allow Trackbacks” checkboxes under the editor
3. You can enable/disable comments here.
In order to access Attachment (image) details, Please follow the simple steps.
– Go to `Media > Library`
– Click on any image, you wish to edit details
– Click on Edit more details
– Here you will find again, Screen Options and Comments control under the editor.
Quick access to Attachment iamge
– Make sure you are logged-in
– Open image you wish to edit, in the browser
– You will find Edit link under the Post, Page or Attachment image
– Click on Edit and you will be on the same screen as explained above.