Check this sign and shirt my brother made with LEDS. The Cinncinati Reds shirt with the C logo in LEDs is made using just two sheets of poster board: one to lay out the design and hold the LEDs and the other to keep the wires from poking the wearer in the chest. There is also a wire running down the seam of the shirt and into your pocket where the on/off switch is. Future design considerations might include making the logo flash "Go Reds!" in Morse code or using a racing lights flashing sequence around the logo.
The Cincinnati Bearcats LED sign (as seen on TV) was made using pieces of foam board. There is a gap in between the piece so security can check it to make sure there are no bombs hidden inside. The LEDs are activated by a switch built into the bottom.