Is it illegal to post naked pics. of your ex on his profile.?

Story short: My ex wouldn't leave me alone, so i took a picture of his... down there part... and made it his profile pic on Facebook for a few minutes. I told him I was going to do this, because I needed sleep as I had class the next day and he would not leave me alone!.:(
Now, his family has threatened to kill me and my family, and i have proof. So i opened a case, and an investigation will be started sometime soon in order to get a protective order put against them. I had to do this, because I'm scared for my life. I just want to know how much trouble I will get into because of what I did.
I know what i did was very wrong, stupid and immature. I wish I could take it back but now i cant and i feel so bad for my actions.
Does anyone know what could happen?