Hello,
You'll have to decide what part and time of the European theatre your dio is taking place ie Normandy, Holland Battle of the Bulge etc and build accordingly. The Bulge was in winter so there will be snow on the ground or heavy mud and was fought mainly in woodland whereas Normandy was.....fought in Normandy where you have farm houses and hedge rows from where your german soldiers can "spy" on the yanks. As for buildings etc, Verlinden do some excellent farm houses etc in 1/35 and Airfix do a command post in 1/72. Any hobby shop online should have a good selection with pictures so you'll have an idea of what you're buying. Have a look at these, they might help especially the 2nd one. Good luck and don't forget to post some pics ofthe finished thing.
Rich
http://www.hannants.co.uk/
http://www.netmerchants.co.uk/section.php?xSec=17
...this is it folks...over the top!