Wow! Thanks everyone for all the great responses. As always it's much appreciated and really helpful. Cheers!
erictacti: I was thinking about doing my own signs, but then I figured I can't speak or read Japanese, so I'll probably do something stupid. I am going to try and keep it fairly close to the original image, without worrying too much if I have to change the odd detail here or there. The blue and white 3D signs were made by cutting out the signs from the original image, messing with the perspective in PS until they looked flat, projecting them onto a plane in maya and then literally cutting them out with the split poly tool. I wanted to try and use the create text tool, but I couldn't figure out how to write japanese in maya or PS.
younglion: Thanks mate. might have to have another look over your car thread to work out how to make my taxis.
tweetytunes: ha ha - yeah, I think pretty much everything in my scene needs a bit more work. Have you seen that seat on my scooter?! And I still need to make some handle bars!
Minstrel: cheers mate! I probably won't do too much detail - only on the objects and buildings in the foreground. I am trying to keep everything to the bare minimum if possible.
Gster: Thanks for the good words. Camera map? I haven't heard of that before. Care to explain?
Thanks again everyone!