Such content is all over the internet. It's not hard to find if you know what to look for. Google Photos is just one of many photo sharing websites used for this. The setup is always the same: a website that only links but does not own content, and either pay-per-click link services or paid for file sharing websites. It's not just Mega. There are dozens of file sharing sites like that. Some stricter than the other. Of course, they all claim to remove illegal content when it's reported, but behind a paywall almost nothing gets reported of course.