I upped the scene description game a little with the most recent two examples I just added to the github repository.
https://forums.developer.nvidia.com/t/optix-advanced-samples-on-github/48410/8
Now the scene description of the rtigo9 and rtigo10 examples allows overriding the camera and tonemapper settings inside the scene description file, but the bigger change was to allow defining emissive materials and lights inside the scene description now.
Previously the environment light and a single hardcoded parallelogram light were toggled inside the system description file. Now you can define arbitrary many lights of different types inside the scene. Still only one environment light of course.
Please read the README.md and the new scene_rtigo9_demo.txt inside the data folder.