GIMP is a great graphics editor, which can be made even better with the addition of a few extensions. Normally this takes a while, as the program has no built-in way to find or install them - but you could always just install GIMP Extensions, which adds more than 50 in a single operation.
GIMP Paint Studio equips the program with additional brushes, patterns, palettes and more.
Plugins include Adaptive Contrast Enhancement, BIMP (Batch Image Manipulation Plugin), Cartoonizer, Focus Blur, GIMP Mask, Image Registration, Liquid Rescale, PAL & VHS, and Save for Web.
Bundled Scripts include AnimStack, Fake HDR Effect, GIMP FX Foundry and Split Studio 3. There's more file format support (APNG, DDS, JPEG XR, WebP). And there's even animation support via GIMP Animation Package. (The full list is available at the GIMP Extensions page.)
You don't have to install all of these, fortunately. If you have some already, or just want to decide for yourself, then the installer allows you to select the extensions you need, and the ones you really don't. And whatever you've selected will then be installed with a click.