I've been talking to my friend Chris about this.
Elves in Fantasy are little more than effeminate Humans with pointy ears and an overly aloof nature.
One more thing Tolkien can be blamed for in modern fantasy (I know I'm going to get hate mail over that one LoL).
In mythology, Elves are far more interesting especially taking on Nordic and Celtic references.
Its quite interesting to note that WizBro attempted to "bring them into the fold" of 4e with Eladrin, but just missed the mark (more to do with the dreadful system than the initial idea).
The "Seelie" (Bright or Good Elves) and "Unseelie" (Dark or Evil Elves) are far more than pointy eared Santa's Workshop midgets or the foppish Drag-Queens of modern fantasy.
By looking around the internet and through dusty tomes you can find a wealth of fantastic ideas about these fascinating people.
The LIST of information about 'real' Elves is seemingly endless, but here are a few thoughts.
An "Unseelie" (as in Evil or Dark) Elf that intends you harm can be "warded" against by marking the doors/windows/entrances with a Pentacle. As in certain Druidic cults the Pentacle is also a symbol of reverence, could a Druid "Turn" an Unseelie Elf with one?
Even though its mentioned here and there, I can't find much reference to the 'famous' Fae vulnerability to iron.
But should you want to include it, how about this - critical hits are delivered to a "True" Elf on a natural 18+ rather than a natural 20+. Representing their weakness towards it. In addition, such Elves cannot comfortably use weapons and armour made from it; and will be at a penalty of -2 to all tasks when wearing it - and cannot cast Arcane Spells at all. BUT (and its a BIG BUT) do we count Steel under this ruling. (Upon saying that, I quite like the thought of Elves running around in cool looking Bronze Armour)
If an Elven Woman is rejected by a Mortal Man or who has lost her Elven Life-Mate becomes a "Beansidhe" (Banshee) - automatically gaining the powers of the Monster and becoming an NPC in the Process. This can be avoided with a successful Save vs Petrification being made once per Month, but a -2 Penalty is imposed on each successful save after the first, till she eventually succumbs to her fate . . . .
Elves in some Celtic Myths have enlarged Canines, much like a Cat (maybe they "evolved" from Felines much in the way we evolved from Monkeys) and have eyes and hair colours that range the full spectrum (it not mentioned, but I wonder if their irises would be 'cat-like' too - a cool thought IMHO). The 'cat' thing might be down to the fact the Ancient Elves were all shape shifters though.
Size - I can't find any solid reference to height! In some cultures they are tiny, others they are almost giants, the Celts described them as "man sized".
Malekith, who was a character from marvel comics - an Enemy of Thor and the other Asgardians was 6'9" tall! (But he is an 'Ancient One') is a shapeshifter (as all Ancient Elves are) and has a vulnerability to Iron. (Malekith exists in Mythology btw, and F'ing GW pinched the name for a Dark Elf Lord grrrr).
Just some thoughts really, though Chris has actually named the movement "CAMRE" (the CAMpaign for Real Elves).
JOIN THE FIGHT!