Free tools for creating textured 3D models usually include Blender (all-in-one 3D workflow and texture painting), GIMP (2D texture editing), and Krita (hand-painted textures for 3D).
Blender lets you model, UV-unwrap, and paint textures directly on 3D models. GIMP is ideal for editing photo-based or seamless textures to apply to 3D assets. Krita excels at drawing custom textures with traditional media-style brushes, exportable for use in Blender or other tools.
For beginners, start with Blender’s built-in tools—they integrate modeling and texturing, so you don’t need multiple apps right away.