RGB LEDs mounted under the tubes give the possibility of cool effects - or, for the traditionalist, these can be disabled to keep the pure, clean glow of the Nixie filaments.
Zen Nixie Clock
This clock by Dalibor Farny is a huge piece of kit. It syncs via WiFi, so once it's set up, it will keep the correct time and automatically resume correct time after being switched off (there's also a rotary controller on the back for manual control).