ps, the unpublished content media files I talk about are shown in the sitemap as "mysite.com/?attachment_id=xxx/"
The unlinked media files I talk about are occurring for the ones I use at my static frontpage, and are linked as "mysite.com/home/name-of-file/. They include both files still on the page (but small thumbnails, intentionally left unlinked, as well as images uploaded to the page and afterwards removed.