Hi,
Recently, I found a great tool on the internet. It is a page that converts measurements from scale to scale, and from full-size to scale, or vice-versa.
The neat part is, you can download the page for free, and use it offline.
The link to it is: http://www.printmini.com/calc.shtml
The site is actually aimed at doll house builders, but it has a bunch of 1/24th scale graphics you can download. Some could be useful in dioramas.
The guy who did this page needs to be recognized for his sharing all this stuff. If you download it, and find it useful, you might email Jim, and thank him.
Thanks,
Mike