sudo

As root

find /srv/lemmy/example.com/volumes/pictrs/files

Find files in /srv/lemmy… that:

-type f

Are plain files (not directories, symlinks, etc; includes images)

-ctime -1

And were created within an amount of time (probably last day, haven’t used this flag in a while)

-exec rm {} \;

For each matching file found execute rm on it (delete it).