Truth is, the expenses for the forum are not that big - it costs Thierry and I a few hundred a year, divided between us, to support the forum -- all spent on registrar fees, forum hosting fees and domain registration fees. We also registered other similar names to this domain so that we don't run into the problem Bruce faces (emovieposter vs. emovieposters), and under different extensions like .biz.
Truth also is this: if I had time on my hands, I would love to promote the site far and wide. Fact is, I just don't have the time to do it. I'm glad we have some good moderators to help out with the day to day. As you have seen, I can be absent for quite awhile when I have cases going to trial or a lot of deadlines to meet. Thierry spends a lot of time here, but he doesn't have the technical know-how, and while his wife does, she's properly busy with working her day job to support Thierry's crack (er, poster) habit.
There is an interesting idea though, that perhaps we create a sister site - not a forum per se, but perhaps a blogging site or some such, and use that as the vehicle to direct more traffic here. I'll dwell on that a bit.
One more thing - Mel's absolutely right that as much as we'd like not to be, we are a mostly movie poster forum. Even the ad posters I collect for the most part relate to movies and movie theaters. Much of the graphic art posters are the same too, relating to movies. Having seen how this place goes for almost a year now, I think we'd have a hard if not impossible time catering to "all posters".
food for thought.