KeepSafe - Keep your entire photo library safely stored in an encrypted private cloud.
Viso - Beautiful minimal image viewer for MacOS
AppLock (FOSS) - A privacy App lock FOSS application.
LightGallery - A modern, electron and nodejs based image viewer for Mac, Windows and Linux.
Hexlock - Security app locker keeps apps private with smart profiles for any situation
digiKam - Professional Photo Management with the Power of Open Source