I took a photo that compares the LilyPad Arduino and a LumiNet node.
As you can see, the attiny84 (the black square on the right device) is smaller than the atmega168 that is used by the LilyPad Arduino. The white box on the LumiNet node is the ultra bright rgb-LED. You can also see 4 pins in each direction. They are used to connect LumiNet nodes with each other. One of the four pins is Vcc and one pin is GND. The remaining two pins are used for communication.
The three (diagonal) pins on the lower left corner and the three pins on the upper right corner are used for ISP programming when needed. If the jumper is removed, the three pins on the lower left corner can also be used as I/O pins. So LumiNet has 8+3 = 11 I/O pins.