I'd do:
Playfield plastic protectors (available in your choice of colors or clear from several vendors)
Speaker lights - gotta do the ones from SpeakerLightKits
Lighted flipper buttons (several vendors)
Real Knocker (several vendors)
Trim completion decals from Tilt
Full color shooter plate from Tilt
Matching Pingulp from Tilt (if you do PinGulps)
Quiet Fan from Pin Monk (wait until you hear the Black Knight start vacuuming inside his castle)