What's your approach to establishing authorship? I'm sure some trolls will try to claim things they didn't actually make and get them removed (and vice versa).
Our initial approach will be to validate the artists manually, and trust them to only flag or upload their own works. If we hit a scale where that starts to become an issue, we have plenty of ideas for mitigating this, but we're not optimizing for that problem yet.
You have no way to stop people from uploading content that isn't theirs. Worse, you have no way to stop your program from stealing uploaded intellectual property.