Unfortunately there's not a lot you can do. You could try to report it for plagiarism if that option still exists and somebody might come and take down the offending upload but I wouldn't bank on it. It's something that has always happened here and it is something that will continue to happen no matter how much effort you put in to try and stop it.
Does it suck? Yeah. Is it unfair? Yeah, but it's par the course with uploading here or anywhere on the internet. If you're not OK with somebody taking and displaying your hard work in their name then you shouldn't upload it to a public space because it'll happen.
The only way to keep something truly yours is to not share it with anyone else.
