-In general, I am against mixing the adds into the poser forum. I don't have the time to keep up with the things I want to follow, and having adds (for me) decreases the value of the forum becuase I have to weed through that much more to find what I want.
--If I find a topic or thread that interests me and I'm already reading through it, and I see a product I like, I would be much more likely to follow a link or otherwise look for the product over on the Product Showcase forum. Really the best way to get me to go there would be for me to see it in action in the threads I follow. (And for the tiny minority of evil types who just thought "hey, I can just pretend to be using my product and get him to follow a link over to it!", that probably won't work. Just slapping in a new thread with a random picture and a link is unlikely to convince me to follow it (there are a lot more links available than I can possibly follow, why would I follow that one?) I already have to be interested enough to get to your topic and stay with it for more than 2 seconds.)
--Of course now that I've said all this I'm going to have to go check out the Product Showcase forum. sleep... what was that?
--This is not a solution to getting people to the gallery, but for merchants who use it and want a way to increase exposure, I would suggest putting a meaningful subject line on the thread. For instance, if I'm looking for hair, I'll LOOK for hair. If I see "now, they're back!" as a subject, I'm not even going to bother looking at it. I have no clue what it is about, and since I have to skip something due to time constraints, I'll concentrate on subjects that appear to be geared towards what I want and ignore the ones that have only a random chance of being anything I want.