These directories are roughly organized by topic. They collect artwork from many people, over many years. One or two were actually done by professionals, but mostly they're amateur. Where possible, the images are in at least two forms: an actual image (JPEG, PNG, ...) and the master artwork. The images based on 3D models don't have many models accompanying them: a bunch of clipart was used and modified and we don't have the rights to redistribute all of that. We'll slowly work out which things we can release. For now, the models of Duke, Tux and the Paper Clip Monster are included.