I was thinking if it would be possible to integrate Flarum with Anonfiles.com API.
This would be helpful to store files externally instead of storing them locally (would solve the lack of file upload features on FreeFlarum for example). I haven't found any extension that does this yet.
It would work like the Imgur Upload Extension - you could upload a file and a link to the file gets pasted into the composer. Maybe there could even be a box with file info and a download button in the post instead of just a plain link. I think that that'd be neat.
Other services such as File.io have their APIs too, which would be an option in the extension itself - therefore, the extension would be called "Flarum External File Upload".