Yup, 60VDC + (neon) ~= 120V diode with a really weird forward characteristic.
Ionization time is in the 10s of microseconds (thus limiting the frequency of a relaxation oscillator to ~100kHz), and light emission isn't very much until it gets well and truly going, so you'd need a truly excellent camera to observe it.
It might be easier to observe ionization directly, using laser beams to detect atomic absorption. Most of the laser beam can be nulled by interferometry, making this much more sensitive than direct emission. It might be hard to create a perspective image of this, but I think it would still be possible. (It would be very hard indeed to do with NE-2s, but a chamber could be set up with the same electrodes and fill gas, and better optics.)
I doubt it's been done before (unless you can find something in an old physics journal?), but it would make a neat graduate research project at least.
Tim