It's almost certainly not real, but even if it's just a badly photoshopped picture of a a real child's face onto an adult body, that still counts as CP.
But I don't think there is really anything that can be done to stop it, banning doesn't work. The mods need to react as fast as possible and delete these posts right away, and everybody else needs to report any post that isn't deleted yet immediately. Unfortunately even in the best case that still takes a few hours.

If we don't want fundamental changes to the site, like requiring an account to post or something similar, the only thing that really helps might be more mods.

Personally, I don't really want to be a mod - but if I could just delete these posts immediately instead of reporting them, I would do that. I have already reported them pretty often (and btw, even that doesn't work through the blocked Tor exit nodes - so the Tor block, that was almost certainly put in place to stop the spammer, hasn't stopped him but has made it much harder for me to report him).

If we are looking for a technical solution, maybe something could be implemented where a certain number of reports automatically hides a post for everybody who isn't a mod, until a mod either deletes it or approves it. But I don't know how many reports you usually get, and as with all technical solutions I don't know how hard it would be to do that either.