Depends what kind of help you want... I've already created suitable speed signs and some tramway signals. Further tramway signals and traffic lights are avilable on the DLS by BOAT. I'm working on various other bits of tramway infrastructure as well, so I'd be happy to help with that kind of thing. I might also be persuaded to have a look at doing some buildings.
Bear in mind that Croydon town centre is now on Google Street view, so there's really good pictures of that area available...
Paul