Hi, Pedro.
My advice is that you have to make the models you want.
Nobody knows why a model is a best seller and another similar don't.
Train stations have the handicap of size. In shapeways, size is price.
Try to show your work in specialized forums, as much, better. Some serious modellers forums are starting to add a section for shapeways in its forums.
But this is a tedious work and I've got very few results.
Model trains is a good activity for 3d printing models. There's many customers from U.S.A. and Germany. But if you want to open market in another country, you have to specialize in this country railroad types. I've doing french railroad stuff for a while, but it's a slow selling market.
I usually work with autodesk inventor, a few with his twin brother solidworks, modelling with the free software sculptris (it's simply and awesome) and coloring and joining models with blender.
Good luck with your awesome work!
Luis