It may help you some to block media from bot instances, such as BotsIn.space. Of course, that may be inconvenient if you or your users follow bots that post images.
You could also import one of the blocklists from Oliphant or another collection. Of course, their purpose is mainly to avoid bigotry and harassment, but depending on how many of them you're federated with, it may have a slight affect on space used as well.
Of course, none of these are even slightly as effective as deleting media server-side, but that's something the Masto.host owner would have to help you with, here.
Want to chack with regulars from the r/wetshaving sub? Join us on [email protected]!
It's awesome to see that there's actually been a wetshaving sub here for two years! However, unless something's not federating right, it looks quite dead now.
On the off chance anyone subscribed to it is still active, use your search feature, search for anything or communities, and enter [email protected]. That's where many of us r/wetshaving folks are moving to.
There are some other subs there as well you may wish to check out, and there may be more in the future. Looking forward to seeing you there!