The only solution I can think of is to do something like this. Put in the board's ToS that posting nudity images will result in like a $500 per fine per picture, that you agree to. Cause it wouldn't be hard to tell who did it. Since I'm sure all the I.P.s are logged. if they use a proxy, it can still be traced, just takes a bit longer. In the end, you can find out who did it basically.
