BJ
Cemetary plots would seem to come in several varieties. Are you looking for a single plot or a more comprehensive family plot?

Typical plants seem to be restricted to Yews and other long living evergreen material. One site though that I know of had thyme planted on the family plots. Apparently the last of the line had ordered a set of thyme plants/seeds and they arrived a week or so after he passed away. The decision was made to sow the thyme over the gravesite and it really does look nice.
Kate

In my area people tend to plant dwarf Alberta Spruce on either side of the stone - a REALLY BAD idea because they are Really-Not-So-Dwarf. These trees cover and upend the gravestone after a few years. Don't do it.

Sedum 'Autumn Joy' on the other hand is the best behaved plant for a cemetery. It looks stylish from early spring when it pokes out of the ground, right through the summer when it blooms, and into December when there is frost/snow on the dried flowers. The only way you can go wrong with this plant is to over-water or over-fertlize it.

I just passed a cemetery the other day when I was speaking in New Hampshire, and the sign at the entry said "No Artificial Flowers - No Plantings" and I have to say that although I laughed at the sign, the cemetery was lovely and peaceful - grass and the headstones...period.

Perhaps memorial plantings should be made in other locations?