Pixabay API - Unlimited API access to 1.2 million CC0 images and videos.
Magnific Popup - The greater part of Lightbox modules will completely preload a picture before showing it.
Sparkbox - Everyone cares about the homepage, but the truth is that it can be a big time suck without a lot of benefit when you tackle it at the beginning of a project.
Fancybox - fancyapps.com - Fancy App Store
Exif Purge - EXIF Purge is a small portable application to remove EXIF meta data from multiple images at once.
LightGallery - A modern, electron and nodejs based image viewer for Mac, Windows and Linux.