If you hadn't noticed already, any pictures shared with or by your friends during a Google Hangouts chat will automatically sync up with Google+ Photos, organized into albums by conversation. These images are uploaded even if automatic back up is disabled inside the Google+ app. New albums can be found under the "Albums" tab and are titled Hangout: [Your Name] ● [Contact's Name] unless you explicitly gave your hangout a title, so you shouldn't have any trouble finding them.
I imagine this feature will provide peace of mind to people who hold mission-critical conversations via Google Hangouts. As for me, I'm afraid it will just be spammy. I organize my photos according to date, and I would be a much happier camper if Google gave me the option to back up my Hangout photos using the same format. Sure, I could log in and rename each album as soon as a picture is uploaded, but I might as well backup my photos manually at that point.
As for those dirty pictures you shared last night? Don't worry, albums are set to private by default. You might want to go retrieve those now.
Thanks, Ikai Lan.