FinderPop just enumerates as files the contents of the following PreferencePanes folders. It merges the contents of these folders into a single menu.
/System/Library/PreferencePanes -- Mac OS X built-in preference panes
/Library/PreferencePanes -- Third-party preference panes available to all users on the computer
~/Library/PreferencePanes -- Third-party preference panes available only to the current user
Unfortunately FP does not know which prefPanes are applicable or not to particular machines or particular configurations. I don't know of prefpane APIs which I could invoke to see whether a particular prefPane should be displayed - this knowledge might well be hardcoded into the System Preferences app. FP just displays all the prefpanes it finds after a bit of tweaking.
Speaking of said tweaking, FinderPop 2.5.5 AFAIR fixes the two instances of 'Printers & Scanners' showing up.
I'll have a look at the icons issue for the next release!