I've seen examples of Photopost being fully integrated into vB, is this possible with phpBB as well? I mean not only sharing database and stylesheets but having the gallery section within phpBB, on the same page.
This would involve you hacking your phpbb files. You can post more about this in the mod forums outside support in whatever forum is most appropriate to see f someone would assist you but basically you need to probally modify the files already present for vb3 to work with your phpbb and include them respectifully whereever needed. I do not run phpBB so I can not say more