Since the Announced thread is locked, here is a new one.
I am not sure how easy it will be to prevent the common idiot from registering, they are not a script or whatnot after all. So what exactly are you changing? If you are adding in one of those pictures that have a blurred word or whatnot in them, many other forum’s have them built-in.
Also, instead of dealing with phpBB2, why not get a good forum, plenty of good ones out there, with upgrade paths from phpBB2. I’ve created mods and even submitted patches for many of them (even phpBB2 sad to say) so if you need help with any, just ask.