Snaptivity - Real-time photo sharing with the world nearby
digiKam - Professional Photo Management with the Power of Open Source
Flashgap - Time-delayed photo-sharing app of last night's embarrassment
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
Poparazzi - Take photos of your friends
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!