Case: 

The whole case was designed in Fusion360 and then 3D printed in a dark grey PLA.

The square hole in the bottom part is to mount an on-off switch and the hole next to it is for the cable comming from the 12V wall adapter. I also put a little support structure on the hole so I could secure the cable with a zip tie.

Schematic:

(Check the pdf in the files section for better quality.)

The clock is powered by a 12V wall adapter. For the IN-14 nixie tubes I used a seperate 170V high voltage power supply, which is mounted under the main PCB and connects via 4 wires.

The rest of the circuit is pretty simple, the µC controls the RGB LEDs, buzzer and the 2 32-bit shift registers for the nixie tubes.

Since the shift registers run on 12V I'm also doing some levelshifting for the control signals.

For the RTC I went with the popular DS3231 again, since it's basicly the perfect device for this kind of application.

To control everything I'm using a rotary encoder with pushbutton.

PCB:

Not much to say about the PCB.

Software:

Source code files are also uploaded, if anyone is interested in looking through the code. I'll probably add some features in the future, like an alarm mode and saving the RGB settings in EEPROM.