Hey, like many of you maybe don't know, there is an "Introduction Forum" where people can introduce themselves etc.
Now, this doesn't fall naturally to everyone, so making a system where you "force" people to introduce themselves (by rewarding it) wouldn't really work, but how about mentioning something like
"Welcome to Diablofans! We would love to know more about you, so if you want to introduce yourself to our other members, please go here and say hello! :)"
Hopefully that can help to the activity of that forum ^^