In Eberron, modern elves are split into many distinct cultures; the Aerenal, the Valenar, the Khorvaire elves and the Drow of Xen’drik. Each of these distinctive cultures have a common shared belief in Ancestor worship but each with a unique twist.
The Aerenal elves worship their ancestors as Deathless, lifeforms much like undead but kept alive by the positive energy of Irian. These Deathless serve as advisers and defenders and are considered by those who worship them to be divine as a whole, in the form of the Undying Court.
The Valenar elves worship only their warrior ancestors. By emulating the deeds of their ancestors, they believe the spirits can live again. They do not resurrect their fallen or beloved as deathless.
The Khorvaire elves are as diverse as the elf race as a whole. They divide themselves by nation or by Dragonmarked House and often follow the local customs though a few still hold their own races believes in ancestor worship but not to the same degree as the Valenar or Aereni. Their half-elven descendents, the Khoravar, have formed a separate community.
The Drow themselves don’t worship ancestors are much as they hold the preservation of their traditions. They view themselves as holding true to their ancestors more then any other by living as they did. The Drow also worship a scorpion god known as Vulkoor, though some Khorvairian scholars suspect this god to be an aspect of the Mockery, a deity of the Dark Six.