Some images have been added to the release notes now. The most important thing we are missing still is images for light and shadowing linking.
- Reference/Release Notes/4.0/Rendering - Blender Developer Wiki
- Reference/Release Notes/4.0/Cycles - Blender Developer Wiki
The Principled BSDF manual page has also been updated:
- Principled BSDF — Blender Manual
- The .blend file and script to generate these is in the benchmarks repository.