As you may guess, the only visualization I am interested in are "oscilloscope" and "spectrum analyzer". They are neither flashy nor cool, but I am interested in the technical content of visualization. The most notably missing feature is the X-Y oscilloscope (or, if it is possible to get it, I haven’t figured out yet how to program it).
Additional oscilloscope views would be interesting, such as a "scrolling waveform" like in high-end audio tools. It could be scaled down to get a preview of the (envelope of the) entire track.
Another interesting visualization would show a one-sided amplitude envelope, such as in professional mixing (DJ-oriented) software. This is well suited to displaying markers too, showing the track structure (chorus/verse/bridge/etc...)
There are fine VST plug-ins available to similar purposes. One solution might be to get a VST to DX adapter and use existing professional VST plug-ins.
I have also found some DirectX plug-ins that perform similar visualization tasks.
There are several DirectX plug-ins for visualization (spectrum and waveform) available
negopus