There was a time when it wasn't obvious to anyone that Google Hangouts was archiving all photos sent to and fro, into albums (much like Whatsapp). During this time, there were also significant others sending... pictures. The Internet generally believed that Google wouldn't be so careless as to post private messages and pictures just anywhere.
Well, we weren't exactly wrong, but when you try to insert a photo in Gmail with this here...
...a dialog appears with photos from every Google-related source: Google Photos, Google+, Hangouts, etc. "Oh hello, ex from 2011... meet... my coworker."
Thankfully this hasn't actually happened... yet. But I attempted to delete all traces of these photos by going through menus in Google Hangouts, Google+, Google Photos, and Google Drive, and I still can't seem to find where the older photos are stored.
How can I delete older photos that appear in the Insert Photo dialog of Gmail?