This is a very cool feature buried down in the ffmpeg documentation that let’s you generate a very nice mosaic of pictures from a video based on scenecuts.
ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
Sample result below
You can also use this to output an individual frame for every video, example follows:
ffmpeg -i ../source/dig_720p.mp4 -vf select='gt(scene\,0.6)' -vsync vfr preview%04d.png
The results of this could be used for a preview track of the video as per the below: