Most of things I thought of was already mentioned, so time for something else ;) Even very well kept cemetaries do not have completely flat ground - you'd need some bumpy ground (TrekkieGrrrl have morphing square and morphing sheet props freebies, any of them slightly morphed makes great ground prop without being too heavy on the rendering speed). Maybe add a patch of grass here and there, that happens on cemetaries too. Good luck, the pic still is a nice start :)

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Outdated gallery over at DeviantArt

Fics at FanFiction.net and Archive of Our Own (AO3)