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.
digiKam - Professional Photo Management with the Power of Open Source
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Polarr - MacOS, Windows, iOS, Android and online photo editing tools & free photo editors.
Capture One - Capture One is an all-in-one photo-editing software that comes with all powerful tools to make your photo editing smoother and more precise than ever.