SharePoint Online - Picture library permissions

So if you wanted to get advanced with flow you could take care of this using it. Here is an older video using HTTP calls direct to ShrePoint, but this was before the new HTTP Request SharePoint action so some of it might be able to be trimmed down, but it's a really good step by step that could possibly get you desired results to automatically assign edit permissions to the creators and read for everyone else.

https://youtu.be/_-vvlPXv8rc

One thing you have to watch for, it takes one person not paying attention to "inherit" permissions on the root level and all your custom permissions go poof. So keep that in mind when messing heavily with custom permissions on individual items and folders in libraries!