Before you sign up you really have no idea what your site is about. You need to sell it first, then allow them to register. Site activity with more network traffic is a good idea. Advertise your site more. Also the board images are a little plain... Theres not a whole lot going on with the visuals. But it's not bad.
I see sites like this all the time on these forums. Specifically forums
And it's no surprise that I'd have guessed you'd make one too, before I even visited your site. However, forums are a great start to a webmasters journey.
If you want your site to be good, then you're undoubtably going to have to put some time into this. I can tell easily who all the newbies are when it comes to this sort of thing. They don't get that the site will not run themselves, no matter how many members you have. Then, after they gain 100+ members, they get bored, and annoyed, and move on because the admins usually fool around and have that careless administrator attitude that most people get when they think their site is "pretty good".
There's lots of things I could say, but most of this is based on the average mistakes that i've seen over and over. Get feedback, add a contact area. Also, you might want to Re-order your forum categories. Why is site feedback in the middle of the forum list? It should be at the top.
Usually you have a section for Administration and Management kind of stuff at the top. Things like site news, announcements, feedback, introductions possibly, help, contact, etc..
Then a section for the main focuses of your site.
Then maybe an off topic area.
Change up your css styles for the forum board, (index.html) The blue headers and the reds do not go together.