I had a look at your forum, and if I were you, I'd move the objects on the front page around. If you must have "images" there, move them to the bottom. The rest of it looks nice but those images take away from it.
There's no quick and easy fix to getting more people posting, but you can make small tweaks like that.
We are actually the remnants of a very old community, so it's not the same as yours.