Up until either the Romatic Age, or possibly Mr Tolkien's Silmarillion, elves, dwarves and other creatures from folklore weren't as well separated or defined. The popular culture (or at least the RPG culture) view of elves were increasingly codified by all manner of published works, from the OD&D books through to Forgotten Realms, with Elfquest and all manner of other things.
Which explains why in every home-brewed campaign setting, while stealing liberally from other sources, elves are either completely 'reskinned', or not changed from the 'original' concept in OD&D.
Anyway, here's the concepts I'm working with for some sort of internally consistent culture, that is 'other' enough, provides some dramatic tension with other species, and has reasons for complicated interactions with these other species. Still not finished, but;
Ancestor Worship; no gods, only one's own ancestors, which means that knowing one's genealogy and family structure is on prime importance. As are family feuds. Being able to 'request' a favoured ancestor to lend knowledge or aid is something all elves are the potential to do, but few learn the deep racial mysteries required to do so. However, many sites of importance are protected by bound ancestor spirits as guardians. Given that no gods = no paradise, those with powerful enough spirits to endure after death don't have all that much to do, and usually welcome the requests of their descendants, within reason and allowing for changes in culture over the ages.
Those that aren't asked presumably haunt their final resting place, but are just as likely to converse with or quiz intruders as attack them.
|Stolen from Warhammer online|
Culture is built around the family structure, and individuals are tightly bound by expectations, duties to others, and obligations. The families are usually insular, and cold and distant amongst all others, aside from other Elven Clans that may offer aid or opportunity. Families are built around the Family Estates - the basis of each clan is one or a series of holdings, with a central sprawling keep and a number of workshops for industries or cultivation. There will be a (to human eyes) amazingly beautifully laid out patchwork of forests, pasture and crops surrounding the keep, laid out in keeping with, and reinforcing, natural landscape features and processes. These provide each family with basic self sufficiency for foods, and each will specialise in one or more crafts, for the glory (and economy) of the family. Up to 500 elves can life in one of these, with up to ten times as many half-elven or human slaves, who are servants, farmers, and basic crafters. Raiding others for slaves is considered work as usual...
Also, the Blades, a small elite force of assassins and warriors who have authority to operate outside Elven Lands. They report to the Royal Couple, but it is rumoured that they are truly loyal to the Mage-Priests.
Roll all this up with an iron cast superiority complex and unassailable self assurance and it should prove interesting.