Image storage for flat file uploads on large sku catalogs

I’ve historically just loaded and updated listing images via seller central but I am going to have a larger and larger catalog and am looking for a good way to make large scale updates to listing images via flat file.

The flat file requires a hyperlink to your images. I would like to have a file structure that allows me to just make updates to the image files and whatever folder they’re in and then upload a flat file that refers to those folder locations so that links all refer to a set of folders.

Just trying to save some administrative time for routine image updates. What tools and processes or hacks are people using for digital asset management on large sku count catalogs?