FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
ACDSee - ACDSee is an image viewer that uses very little system resources, and it has a small, sleek size that won't take up much space on your system.
Zoner Photo Studio X - Zoner Photo Studio X is a full RAW editor and image organizer software. It features a bit-map editor with layer and mask support, a video editor and a full module dedicated to culling, cataloging and complex metadata management.