Environmental Interactive Graves
Here's an idea. Adding a metal sculpture of a cow or goat horn as a permanent addition to a gravestone. Make sure that it can function as an instrument and position it so that the wind can blow through it. After installation then anoint it with water which has had pieces of an actual such horn boiled it in. Do this repeatedly each time you visit. Eventually according to the occult principles of similarity and contagion the metal horn will become magically the same as an biological one. Enchanting it then would allow the sculpture to summon the spirit of a cow to provide milk to feed the spirits of the dead present in the burial place.
Furthermore the sound of the horn is sure to create an eerie atmosphere in the location. This could help ignite interest in new forms of cemetary decoration, fuel local urban legends, and create a interest in tours (which could be used to help fund upkeep especially in older places), etc. Another idea which I have toyed with is somehow finding a way to incorporate a drum sculpture somehow which would be played when raindrops fell upon it.
Note: Make sure to have obtained legal permission from all necessary parties first.