Just for interest sake, how long has your Discourse site been live and what size is your current backup file. I’ve just started up a new site with Discourse which is going to involve lots of image uploads so just wondering where you stand after X months. @codinghorror solution was indeed what I was thinking to do is every month run a cron and compress all images older than X months using littleutils or any other image compression software. Littleutils handles PNG’s quite well and is used as the backend to a number of Wordpress image compression plugins.