A nice effect to have in your graveyard is a freshly dug grave. If you don't want to dig a hole in your yard or just dig/till some dirt up try this...
Use a piece of plastic, it don't matter what color, and lay on the ground where you want the dirt to be, then by using dirt out of your garden, or some place where you won't get in trouble, or with a bag of potting soil, pour on top of the plastic, place your tombstone where it looks good to you and presto! Fresh dug grave!
For a little extra effect add a shovel and a lantern (with battery Christmas lights in it), or even a few bones or body parts next to your grave.