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.
Ralpha Image Resizer - High-speed image batch conversion tool
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Polarr - MacOS, Windows, iOS, Android and online photo editing tools & free photo editors.
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.