First off I would like to say that I wasn't quite surpirsed by checking your work out. It's not difficult, and not too simple, either. I, myself, am not able to create unique things, or a bit more stylish work as some of the guys above mentioned, however I can more or less create the same thing and I was truly excpecting something cooler. :>
I remember building the same thing a few months ago on Minecraft. Of course, not the same 100 percent, but I had a similar building, also used cabble-stone, only. I think that adding windows in some of the walls, would make it look better, in a way. As well with that, try creating big entrances, for example and entrance for trains (put train train tracks), create a big entrance for people; preferable iron doors to match the colors, and not wooden doors. Other than that I can only say congratulations on finishing your project, and good luck adding things to it!