Nixie tubes will never go away, instead they live on as displays in bespoke clock projects like the following vertical model by Andrea Biffi. It's great to see that Andrea has not stopped at just making a bare clock circuit, but instead has put in the extra effort to craft a housing that befits these antiques of the electronics world.
From an electronics perspective the circuit is a typical Arduino-compatible with a real-time clock IC, with a classic boost circuit to create the high voltage for the Nixie tubes. To facilitate others in making their own version, Andrea has published the schematics and bill of materials to save you searching for the correct circuit. Then it's up to you to find the tubes and create a unique housing, for example:
The most important part of any clock project is the inclusion of an accurate real-time clock IC. Here at Freetronics we have the Maxim DS3232 real-time clock IC module:
Apart from keeping accurate time for years due to the temperature-controlled oscillator and having a tiny coin-cell for backup, it is very simple to connect to your Arduino project. A driver library allows your program to easily set or read the time and date. Perfect for clock projects, dataloggers or anything that needs to know the date and time. Furthermore it contains a digital thermometer and 236 bytes of non-volatile memory to store user settings and other data. For more information, check out the module page here.