Making your own gravestone is as easy as shopping the after summer sales or keeping your eyes open. I prefer to use swim kickboards that can be picked up at department stores and some grocery stores. A can of black and gray spray paint or a sponge and tempura paint and some craft paint brushes can scare up a truly deadly grave marker. Apply a base layer of paint but after that do not try to be perfect, dab on the paint haphazardly or spray in the same manner. You will create a misty, aged look to your gravestone. Paint on a cryptic message or a creepy name and dates and you can be finished. Only your creative desire will tell you otherwise. Use some clip art to paint on bats, cats, or witches or drape your stone with some cobwebs made from cotton balls or batting. Cheese cloth can look like mummy wrappings snagged while the grave's former occupant left to find a meal. Use some potting soil scattered in front for a more authentic cemetery look.