I've just uploaded a collection of iTunes scripts that enable growl
notifications (among others), you can download them all in the files
section (the folder also includes unedited default iTunes scripts). I
suggest replacing the scripts in ~/Library/Application Support/
Quicksilver/PlugIns/iTunes Module.qsplugin/Contents/Resources/Scripts
with the contents of the folder.
If anyone has any suggestion/additions to the scripts, I would be more
than glad to accommodate that. More icons would be especially welcome.