Funny enough, MoviePy makes it so easy to edit videos that we also use it to edit images. But the way it works is when a user uploads an image, we convert the image into a video format, edit it with MoviePy, then convert it back into an image. A little inefficient, but it works better for us than writing a completely different branch of code to handle images.
Having worked with MoviePy for a while my main ideas for improvement would be: 1) Create a callback for video editing progress so that it could be outputted to the frontend, etc, 2) Make predefined transitions - currently transitions need to be manually calculated, would be nice to have smarter presets to make it easier to create something like a slideshow, 3) improve threading over multiple CPUs - not sure how possible it would be for the library itself to handle this but from our initial tests ffmpeg by itself seems to handle threading more effectively