So to make fun with the trainz you need something useful for them to do.  I propose a teensy iron mine on one end, and a iron furnace on the other...a tiny cute little furnace like these;  I think it could be miniatureized, backed against a hill and have a nice little waterwheel feature too.  and I think the led from one of those small battery tea candles could be robbed to make a realistic "fire" effect in it.