I just uploaded version 0.15.0 to extras devel.
This version adds two Nixie Tube image sets based on the images rotoflex linked.

@Mentalist Traceur
Did you get your issue resolved?
I changed the way Advanced Clock Plugin hooks itself into the system because I got some reports about people having issues with the old solution.

The old solution was that I used sed etc. to modify "/etc/hildon-desktop/status-menu.plugins".
Now I am replacing "/usr/share/applications/hildon-status-menu/clock-plugin.desktop" with my own version and keeping a "backup" of the original one in "/usr/share/applications/hildon-status-menu/clock-plugin.desktop.distrib".
Unfortunately, my first attempt was not working correctly.
Version 0.15.0 should fix this issue.

I attached the original clock-plugin.desktop file just in case someone messes up its own as I did while struggling with that issue.

@skykooler
Yes, that's the issue I meant with respect to transparent areas in animations.
As for a quick fix:
Would it be possible to surround the images with some kind of frame such that there are no transparent areas in the animation?

I tried to find a better solution ever since I am aware of this issue.
Though, unfortunately I didn't find a satisfying solution yet.
I had one approach that used a rectangle on a cairo context to "overdraw" the last animation frame with "transparency" (basically erase a rectangular area in which the animation happens) prior to drawing the next animation frame.
Though, this approach caused the animation to flicker.

Maybe someone with more expertise in (py)gtk pixbuf and drawable/drawing area has a better idea?