Mat/Thomas,
I recently needed lots of icons to represent business units, document Libraries, Team Sites, registries and more with multiples required due to the permutations.
After going crazy trying to find Icons, that were both suitable and had some aesthetic consistency I struck on an idea related to Thomas's I Found SVG icons that were hollow or suitable for overlay some examples with the sub picture added attached;
Using inkscape it is simple to import other svg or png files into the first image and resize, save as SVG or export as PNG
To follow mats original suggestion perhaps we could add a select set of "hollow" svg icons and an a set of icons that can be overlaid and scaled programmaticaly thus obtaining a large set of possibilities from a smaller set of icons.
To assist it may make sense to use a system like the language translations so there is a set of image names that can be inserted and the user chooses what represents what name and the selected image is applied to the locations where the image name is used.
This would make icon sets transportable and quick to set up.
Regards
Tony