digiKam - Professional Photo Management with the Power of Open Source
Prisma - Art filters using artificial intelligence to transform your photos into classic artwork.
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
Brillar - Bring glitters, stars and sparkles to your videos and photos.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
A Color Story - The photo app to colourize your life