Editly has a simple CLI for quickly assembling a video from a set of clips or images, or you can use its more flexible Javascript API.
https://github.com/mifi/editly
Example:
editly \
title:'My video' \
clip1.mov \
clip2.mov \
title:'My slideshow' \
img1.jpg \
img2.jpg \
title:'THE END' \
--fast \
--audio-file-path /path/to/music.mp3
#js