I browsed the rules, and I can't really see any that would specifically outlaw fakes except for maybe one:
Is intended to sexual objectification of another user without their consent.
The fact that this thread exists and isn't in violation of the rules should mean that stuff dealing with sexualization of celebrity figures and popular online personalities isn't in violation, and there's nothing in the rules specifically addressing photomanipulations. There's also
Depicts any person without inspecting and maintaining written documentation sufficient to confirm that all subjects of your submissions are in fact eighteen (18) years of age or older, including a written consent or release of each identifiable person in the submission to use their name or likeness and to enable inclusion and use of the submission in the manner contemplated by LPSG and these Terms.
But people post pictures of celebs and online personalities over 18 on here without them giving express permission to post on LPSG either, so I don't see why fakes would be against ToS unless there's something in there about it and I'm just blind