Good point, @tophee. I forgot about the change for assets.
These settings govern if and how long an unreferenced image will persist:
clean up uploads
Remove orphan unreferenced uploads to prevent illegal hosting.
purge deleted uploads grace period days
Grace period (in days) before a deleted upload is erased.
clean orphan uploads grace period hours
Grace period (in hours) before an orphan upload is removed.
However, I don’t know if having the image referenced in the “Welcome” topic counts as a reference.
More in this topic: