Your site is like a mile long, and your forums theme does not fit the topic of the page. Things need to be streamlined a little better then what they are. Regardless if you attract people, you need to keep them around. I visited your site and see no reason to go back. To be honest, your site looks like its something you threw together overnight. The site is supposed to be about horror, such a horror movie and books? What is Tokusatsu?? I can not even pronounce that! And what is Sentai?? Are you trying to attract japanese traffic or english traffic? Your site needs a total redesign and your forum needs to be done the same way. Even if you did get a lot of traffic, they probably are not going to stay, much less sign up on the forum. Besides that I would start out by making my own spoof horror films and posting them on youtube. There are a lot of directors that make series for youtube in 10 minute segments. Google video allows longer then 10 minutes, so maybe post your own videos there. Become a youtube partner, then you can upload videos about 20 minutes long, as compared to 10 minutes. Metacafe is a nice place to post your own homemade videos. I have seen some high quality stuff there. Works like frankstein and dracula should be out of copyright protection. You should be able to make your own videos based on those themes, post them on youtube, get a fan base going on and drive traffic to your site. Install some video embedding software in your forums, then embed your videos into your forum threads. This will give guest to your forums something to watch. Click on the youtube channel link in my signature and you will see how I use videos to promote my site.
Thanks for all the replies, guys I've not got time to reply at the moment but I plan to come back here in a while and address all the issues brought up so thanks!