POV displays are one great way of getting large images with only few LEDs. Spinning object with LEDs in them you can display messages, graphics and various effects. People like these things on bicycles, because it is fairly easy to build, but most important it makes you look different.
Balrog-k1n have shared his bicycle POV implementation. In his project he uses Arduino to send images through six WS2811 LED strips.
To give his creation interactive control and sense, he used 6+DoF sensor board which comes with Accelerometer, Gyroscope, Magnetic field sensor and barometer. Not all sensors are used here. In order to change light patterns he used neat method – since there are IMU unit, he can send control signals by taping breaks at different patterns. This doesn’t work 100% reliably, but seems it is enough to do the trick.