Gravestone

An urn or gravestone appears on the lot when a Sim dies. An urn can be placed on the floor or on tables and counters. A gravestone can be placed on the ground outside. Sims can "Mourn" over graves or urns. With Nightlife, they can be moved to a community lot.

In The Sims 2, if a Sim had a platinum status when he/she died of old age, a gold gravestone/urn will appear and if you look closely at the gold urn the dead Sim's aspiration symbol will be on it. If your Sim had a disturbed or troubled life, where few wants were fulfilled or many bad things happened, this will result in the average, gray gravestone/urn.

In The Sims 3, the plaque on the gravestone shows how they died:

Lightning Bolt: Electrocution

Hand sticking out of a pool: Drowning

Flame: Fire

Hourglass: Old Age

Fork and Knife making an "X": Starvation

Sphinx: Mummy curse

There are at least 3 different types of graves in the grave yard that comes with the game, a flat plaque like one, a tall obelisk type and another similar to those in The Sims 2. A Sim can obtain these different gravestones by:

Small Plaque

dying without completing lifetime wish;

Medium Grave

dying after completing lifetime wish and having earned 50,000 - 150,000 lifetime happiness points;

Large Tombstone

dying after completing Lifetime wish and have earned 150,000 or more Lifetime Happiness points.

You have the option of whether to keep the grave on the Sim's home lot or to put it into Cemetery.