Although you probably won't see a U.S. Army (Navy) (AirForce) decorated locomotive in mainline service, switching units were/are seen on larger military bases. Depots and Supply Centers shift large volumes of cargo by rail and Department of Defense owned equipment often gets the job of switching these cars locally. Almost every kind of railway car would fit a military train. Flat cars with armor , trucks, and guns easily come to mind. But the military also needs beans with those bullets. Box cars, covered hoppers and coal for power plants are approriate for military locations.
Modeling a military base is pretty simple. Structures seem to have that "low bidder" simplicity.
Generally wooden frame structures are approprate structures on military bases that date back to World War II. Many of these were around well into the 1990's and a good many still stand. Temporary structures (tents) are available from at least one manufacturer (Roco) and semi-permanent (Quonset huts) are made by several vendors. For newer permanent buildings, steel industrial buildings will do with the ocassional concrete structure. Adding military figures and vehicles gives almost any scene the military flavor. Top it off with a lot of chain link fence. You can make miles of it around your scale model military base with a dollar's worth of "tulle" (wedding veil) from a fabric store. And don't forget a few German Shepard guard dogs along the fence line.
Everything you need is out there. If you don't see it at your hobby dealer, just ask. And don't forget the flag!
