I don't think threatening to reciprocate the blackmail is something I'd ever want to do, both for moral and legal reasons. I don't think they'd fire me for being a blackmail victim, but I wouldn't be surprised if they fired me for creating an uncomfortable work environment should my coworkers receive those photos.

You wouldn't be the one creating the hostile work environment, that would be on the perpetrator of the crime, as others have said file a police report and inform your HR department as to what's going on. You'll be fine.