Dibuja - Gtk based basic paint program like MSPaint or Paintbrush but for Linux
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
Corel AfterShot Pro - Say hello to Corel AfterShot Pro 3, the world’s fastest photo workflow tool! Edit your photos up to 4x faster than Lightroom so you can spend more time behind the camera. Download a free 30-day trial today!