Here is a really cool idea: tiny light-emitting diodes (LEDs) in a variety of colours fitted with a minuscule circuit board with components that harvest energy from an inductive charger as used by mobile devices. These allow applications where you want to place lights on an object wherever you like without the fuss of running (and hiding) wires everywhere. They are popular with modelers, who can embed the transmitter coil in an object, then place lights freely on its surface.
I’ll bet you could drop a bunch of these on one of those McDonald’s tables that has a built-in wireless phone charger and they would light up.