> You could use (cleverly-braided+insulated) regular LEDs if there was a breadboard or something behind the map, but that'd be both huge and inconvenient.
Theres a simpler solution that uses the same idea. Have pins that look like mono audio jacks, so the "tip" and "ring" are separate. Put two layers of conductive material down on the map, one on each side of the insulating board, and apply a voltage between them. When you stick in the pin, your "ring" contacts the closest layer, the tip the furthest, and so you have a voltage available to power the LED in the head. The voltage would only need to be about 3V or so, so its perfectly safe, you just need a small fuse in case of shorts.
Manufacturing a conductive "ring" on a pin would be difficult with machining, so using a conductive paint on top of an insulating paint would be the best option. The hardest issue would be ensuring a reliable contact with the ring, as the contact surface would be very small.
Theres a simpler solution that uses the same idea. Have pins that look like mono audio jacks, so the "tip" and "ring" are separate. Put two layers of conductive material down on the map, one on each side of the insulating board, and apply a voltage between them. When you stick in the pin, your "ring" contacts the closest layer, the tip the furthest, and so you have a voltage available to power the LED in the head. The voltage would only need to be about 3V or so, so its perfectly safe, you just need a small fuse in case of shorts.
Manufacturing a conductive "ring" on a pin would be difficult with machining, so using a conductive paint on top of an insulating paint would be the best option. The hardest issue would be ensuring a reliable contact with the ring, as the contact surface would be very small.