Is there a screenshots scene writing guide?
You mean like putting in images and pictures? If so there should be a guide in the advanced techniques part of the choicescript tutorial
Copy the scene into a new file, change all the *choice to *fake_choice, set all your stats just before the scene and delete everything else. String together the screens you want to show.
This way CoG can flip through 5 scenes without playing the game itself. Change up the stats to showcase variety and pick your favourite scenes that best show your game.
CoG does it from there, taking screenshots of each scene for various devices.
Who is the prospective audience for this?