It works, however, obviously it's very limited. You only get a new banner when you enter the forum. going to any topic will bring up the default banner. I had this problem worked out in 3.3. Please take a look at the following page to see what I mean.
The old code was looking for a "forum ID" number in each page, and by adding that to the drop down paging, and topic.asp etc I had it working pretty well.
When it comes to 3.4 though, I'm pretty much at a loss. being a newbie I'm not sure what exactly your code is doing, but it doesn't seem to be looking for a "forum ID" on every page. If you could somehow change it to that, then you could probably use the rest of my code to make the right forum banner show up every time. (eventually I even got this working in active topics).