Flickr - image and video hosting website
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Imgur - Imgur is a free and simple image hosting service with image editing feature. Signup is optional.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
Google Photos - All your photos are backed up safely, organized and labeled automatically, so you can find them fast, and share them how you like.
IrfanView - IrfanView ... one of the most popular viewers worldwide.