Photos & Graphics
The arts of photography, graphics creation, and image editing have forever been changed by modern software such as Adobe Photoshop. It’s now easier than ever to have total control over every single aspect of a photo or other graphical image, with the ability to export and share whatever still or moving image you want.
Most popular apps

GIMP
GIMP is a free program for such photo retouching, image composition and image authoring. Essentially it's the closest thing to Photoshop you can get for free.

Inkscape
Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format.

Krita
Krita is a professional Free and open source (FOSS) painting program. It is made by artists that want to see affordable art tools for everyone within concept art, texture and matte painters, illustrations and comics.

Blender
Blender is the free and open-source 3D creation suite. It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing, video editing, and motion tracking.

Adobe Photoshop
Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Windows and macOS. It was originally created in 1988 by Thomas and John Knoll.

ShareX
ShareX is a free and open source program that lets you capture or record any area of your screen and share it with a single press of a key. It also allows uploading images, text or other types of files to many supported destinations you can choose from.

Paint.NET
Paint.net is a free and very capable image editing software for Windows. Great alternative to Photoshop for people that do not need all the stuff PS offers.

IrfanView
Fast and compact image viewer/converter trying to be simple for beginners and powerful for professionals. Many supported file formats and features. Features included: multi-language support, Thumbnail option, Painting, slideshow, toolbar skins, fast directory browsing, batch...