" Also note that so far the single-pic icons work, the multi-pic don't."
What is a multi-pic ??
It's not an official term, but ...
An icon like klipper.svgz is a compressed version of one single image in Scalable Vector Graphics format, which means that it is actually a gzipped text file defining how the image should look.
The look of audio.svgz, on the other hand, varies depending on the volume settings in kmix. Traditionally such variations have been achieved by using several different icons. (E.g. one icon for a full trashcan and one for an empty one.)
In the case of files like audio.svgz, however, all the different versions of the icon are to be found in the same file/archive, so audio.svgz actually contains five different pictures. They are all easy to edit with Inkscape, but I haven't been able to create the archive in such a way that the icon would work as intended.
I simply don't know enough about the SVG format yet, and I've only used Inkscape for an hour and a half.