what happens when you clear pictrs? you mean just deleting the folder? does that break stuff?
for comparison, my instance is only communities and no users (FAQ here: https://programming.dev/post/442419 )
it's about 5 days old but not much activity
# du -h --max-depth=2 ./
73M ./volumes/postgres
7.8M ./volumes/pictrs
8.0K ./volumes/lemmy-ui
81M ./volumes
81M ./
the latest backup is only 7.4 MB zipped, I use this backup script
#! /bin/bash
# https://join-lemmy.org/docs/administration/backup_and_restore.html#a-sample-backup-script
now=$(date +"%Y-%m-%d_%H.%M.%S")
cd ~/lemmy && (docker-compose exec -T postgres pg_dumpall -c -U lemmy 1> dump.sql 2> dump.errors)
cd ~/lemmy && zip -r9 ~/bak-lemmy-$now.zip ./ --exclude "volumes/postgres/*"
rm -f ~/lemmy/dump.sql
like I said though, not much activity
and here's how my backup zip files have grown in size over time
6.6M bak-lemmy-2023-07-08_03.00.01.zip
6.6M bak-lemmy-2023-07-08_06.00.01.zip
6.6M bak-lemmy-2023-07-08_09.00.01.zip
6.6M bak-lemmy-2023-07-08_12.00.01.zip
6.6M bak-lemmy-2023-07-08_15.00.01.zip
6.6M bak-lemmy-2023-07-08_18.00.01.zip
6.6M bak-lemmy-2023-07-08_21.00.01.zip
6.6M bak-lemmy-2023-07-09_00.00.02.zip
6.6M bak-lemmy-2023-07-09_03.00.01.zip
6.6M bak-lemmy-2023-07-09_06.00.01.zip
6.6M bak-lemmy-2023-07-09_09.00.01.zip
6.6M bak-lemmy-2023-07-09_12.00.01.zip
6.6M bak-lemmy-2023-07-09_15.00.01.zip
6.6M bak-lemmy-2023-07-09_18.00.01.zip
6.6M bak-lemmy-2023-07-09_21.00.01.zip
6.7M bak-lemmy-2023-07-10_00.00.01.zip
6.7M bak-lemmy-2023-07-10_03.00.01.zip
6.7M bak-lemmy-2023-07-10_06.00.01.zip
6.7M bak-lemmy-2023-07-10_09.00.01.zip
6.8M bak-lemmy-2023-07-10_12.00.01.zip
6.8M bak-lemmy-2023-07-10_15.00.01.zip
7.0M bak-lemmy-2023-07-10_18.00.01.zip
7.0M bak-lemmy-2023-07-10_21.00.01.zip
7.0M bak-lemmy-2023-07-11_00.00.01.zip
7.0M bak-lemmy-2023-07-11_03.00.01.zip
7.0M bak-lemmy-2023-07-11_06.00.01.zip
7.0M bak-lemmy-2023-07-11_09.00.01.zip
7.0M bak-lemmy-2023-07-11_12.00.01.zip
7.0M bak-lemmy-2023-07-11_15.00.01.zip
7.4M bak-lemmy-2023-07-11_18.00.01.zip