@Gargron might consider putting a default of say 30 days into the first install. Setting up a new server is a bit complicated/confusing if you haven't done one before.

Getting your head around everything on day 1 or even day 30 is hard when your focus is on building connections with follows, relays and maybe #FediFetcher. Otherwise it's a recipe for a storage blackhole. Given images can be re-fetched on demand it seems pretty obvious.

Might even save setting up a S3.