FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Priime - Edit photos with the styles of the world's top photographers. Smart suggestions, fast editing, and inspiring collections.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Nizo - A better iPhone camera for shooting film
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
VSCO Cam - VSCO Cam is an iPhone, iPod Touch, & Android camera app w/ elegant, minimal processing options.