Nope, it's a flat panel LCD and yes, that image's background causes it too.
Hmm, interesting, I just dragged the image onto my other monitor and it doesn't shimmer there.

The only difference between the two is that one is size, one is 18", the other 17", but both a re displaying 1280x1024 @60Hz.
Hmm, just checked in Nvidia settings and it turns out they are not both running at 60Hz, only the 17" one is...
Hah! KDE Display reckons they're running at 50Hz
Well, I'm not going to mess around with it now, that will have to wait for the weekend.