This was just testing to see what could be done.
With only 1.5v the LED was dim (on the train it gets roughly 6v), so if you want an impressive light you need more volts. You also need some way of turning the lamps on or off, so if you have a number of lamps then a common power source with a switch is the answer. With just one lamp, an appropriate battery hidden away which you just connect or disconnect would work.