Seems there are quite a few different ways people are handling this.
I create a SOURCE titled something like
Grave marker at XXXX Church Cemetery.
Then citations are created for each gravestone of a person at that cemetery in my database. I attach these citations usually to the DEATH and BIRTH facts--the dates being key data (I don't keep BURIAL facts), but you can attach them to any fact for which the info on the stone applies. If there is a second or more people on the stone/marker, the it is easy to just "link to an existing citation. The Citation text field includes ALL of the writing on the marker.
Pictures of the marker are attached to the citation.