Free Options for Computer Generated Imagery:
Hexagon from Daz provides a basic 3D modelling package which is intended for creating simple props for Daz but makes a great place to start objects to transfer later to more sophisticated software such as Maya that you cannot afford or run on an older PC/Mac. Also ideal to create items to 3D print since it can export as .stl Documentation + Tutorials
Texture Haven provides some great free Creative Commons textures in up to 4k resolution.
Image Manipulation and 2D Paint Software
GiMP Image Manipulation – the open source Photoshop rival.
Fire Alpaca is a lightweight app for Mac and Windows which will run fine on older machines too. See Youtube video. Does contain advertising, which requires payment to SE Windows version through Steam to remove.