I'm going to preface this by saying that I have a tendency to come across as a jerk when writing forum posts late at night, so please don't take it the wrong way if I do come across like that.
Executive Summary/tl;dr: I think you probably have too many forums and subforums. You should consider reducing the number in order to make it easier for members (especially new members) to navigate and to keep the content more vibrant and engaging.
I know it's kind of weird that this is my second post and I'm already making suggestions, but this is from my (admittedly limited) experience managing forums and doing web design (which I have quite a bit of formal to informal experience in).
Anyway, I noticed that you've been talking quite a bit about how to keep people coming back, and I think I can solve your problem for you. Basically, I think y'all have too many forums and subforums. I've been a forum admin and moderator in the past and this is something that I see a lot which I think causes problems which might not seem obvious. Basically, your forum is really small right now. No, it's not tiny, but think of it this way: you have 512 topics and 25 forums, plus more subforums than I felt like counting. That's a problem, because what you end up with is, as Chris Sanders puts it, an embarrassment of riches (although I like to call it "community dissection"). New members (myself included) show up and are overwhelmed by the number of forums. Just as a comparative example, recall what you thought when you first realized how long this post is. If the first thing on your mind was to the effect of, "Holy crap, I really don't want to read all of that," you experienced the same thing that I think a lot of new members experience when they first come here.
...recall what you thought when you first realized how long this post is. If the first thing on your mind was to the effect of, "Holy crap, I really don't want to read all of that," you experienced the same thing that I think a lot of new members experience when they first come here.
Even though you only have one forum with zero posts in it, most of your forums have very few and a number have ten or less. The reason this happens is because there is enough overlap between your many forums that posts which could very easily be grouped together are spread out over several forums and, as a consequence, people looking for topics of interest basically go to the few places that jump out at them and then leave, because there are too many subsections for them to check and not enough time, causing them to miss topics that they might have seen and replied to, otherwise. (The "new topics" button doesn't count - even if users know about it, it still becomes an issue when people are making new threads.) Look at any successful but small forum (a good example is one I frequent,
abletonlivedj.com/forum, note how there are only 12 forums (you'll see 11, one of them can't be seen by people that aren't logged in; sorry) that invite constant posting and how almost all of them have a good deal of posts).
I really, really, strongly urge you to merge or eliminate a lot of boards here... the more boards you have... the less time they spend on your site
Another issue is that a lot of your forums here are really redundant with each other (ex. "Time to Chill" really is the same thing as "General Board" and there are so few posts in "Fun and Games" that that could really go under "General Board" as well). Just in general, that's not a good thing in any timeframe, because in the short run, it leads to confusion over what goes where and, in the long run, it means that you're going to end up with three forums with identical subjects and similarly-intentioned posts spread across all three, making organization a nightmare.
I really, really, strongly urge you to merge or eliminate a lot of boards here, just for the sake of clarity and efficiency. It might sound counterintuitive at first, but I know from personal experience that, the more boards you have, the less content people actually look at and the less time they spend on your site, which is the opposite of what you want. You get the same effect as a massive, wall o' text post like this one, where it's simply overwhelming, which leads to people tuning things out. A lot of things.
Personally, I would drop the forum structure down to something more basic, like this (asterisks (*) designate categories, dashes (-) designate forums and multiple dashes designate subforums):
*General
-IMPORTANT INFORMATION
-General Board
--Games
*How to Train Your Dragon
-How to Train Your Dragon (locked forum)
--The Film
--The Book
-Spin-Offs
-Fanart
*Other Media
-Dragon Related
-General
*Roleplaying
-HTTYD RP
--Rules
--Characters
That takes you from 25 top-level forums to seven, which I guarantee you will be a lot easier for everyone.
Also, not to sound like I'm trying to hard sell you on this, but I feel the need to point out that, the sooner you reorganize, the better, since ProBoards doesn't seem to let you move posts
en masse and that means a lot of manual work, which sucks and sucks even more when you have to do a lot of it. (I know ProBoards lets you make specific groups only able to do certain moderation functions, so if you're interested but not really excited to do the work yourself, you could probably set up a temporary group of movers to get the bulk of post moving accomplished.)