This decorative snowflake can either be laser cut or 3d-printed. There's a hole in the center that's just big enough for a 5 mm LED. You might see the 220 Ohm current-limiting resistor in the picture (soldered to the cathode of the LED). Other similar values will also work for +5V (USB) and a white LED. Use smaller values for brighter light. For instance see which resistor to use.

This year, the lights in our Christmas tree are LEDs, powered by a USB charger.