I don’t know if Lemmy is a good idea. The way Lemmy handles images is pretty bad, and that makes it hard to moderate: Allow all admins to purge content · Issue #2976 · LemmyNet/lemmy · GitHub
Last I checked, whenever you upload a image to Lemmy, Lemmy just gives you a url to the image. You don’t even have to publish the post to keep the image uploaded. That, and there isn’t any way to trace the image back to its original post or even user.
A couple of times (that I know of) what happened was one of the main Lemmy instances (lemmy.ml?) was being used as a cdn for csam under the admins’ noses and one of those times got them taken down for a couple of days due to an automated report.