Open-Source Graphics Copy collection link

This set includes versatile tools for graphic design, photo editing, and illustration, all available for free.

Krita Foundation
Krita is a FREE and open source painting tool designed for concept artists, illustrators, matte and texture artists, and the VFX industry. Krita has been in development for over 10 years and has had an explosion in growth recently. It offers many common and innovative features to help the amateur and professional alike.
Martin Renold and the MyPaint Development Team
MyPaint is a simple drawing and painting program that works well with Wacom-style graphics tablets.
Inkscape
Inkscape is a Free and open source vector graphics editor for GNU/Linux, Windows and macOS. It offers a rich set of features and is widely used for both artistic and technical illustrations such as cartoons, clip art, logos, typography, diagramming and flowcharting. It uses vector graphics to allow for sharp printouts and renderings at unlimited resolution and is not bound to a fixed number of pixels like raster graphics. Inkscape uses the standardized SVG file format as its main format, which is supported by many other applications including web browsers. It can import and export various file formats, including SVG, AI, EPS, PDF, PS and PNG. It has a comprehensive feature set, a simple interface, multi-lingual support and is designed to be extensible; users can customize Inkscape's functionality with add-ons. The Inkscape project has a growing international user community, and many learning materials exist to help get you started with your creations. Help and support is provided by the community, and there are lots of ways for you to get involved if you want to help improve the Inkscape project. Inkscape is a member of the Software Freedom Conservancy, a US 501(c)(3) non-profit organization. Contributions to Inkscape are tax deductible in the United States.
The GIMP Team
GIMP is an acronym for GNU Image Manipulation Program. It is a freely distributed program for such tasks as photo retouching, image composition and image authoring.
dotPDN LLC
Paint.NET is image and photo editing software for PCs that run Windows. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. An active and growing online community provides friendly help, tutorials, and plugins.
Orama Interactive
Unleash your creativity with Pixelorama, a powerful and accessible open-source pixel art multitool. Whether you want to create sprites, tiles, animations, or just express yourself in the language of pixel art, this software will realize your pixel-perfect dreams with a vast toolbox of features.