Just an Elvish sound is fine, and I guess Tolkien's would be suitable - it probably sounds the same and even I'm not enough of a geek to tell the difference (if you look at Welsh written down, which most Elvish is in the game, it looks like it should sound completely different to how it actually sounds!)
To the poster who wondered how it was recorded (in the other thread I accidentally created), it is all written in Propellerhead Record 1.5 with Reason 5.1 (which most commercial electronic house/pop/r'n'b etc is written on). At the moment the tune is just a sketch that I've been playing with for an afternoon.
I would go with Tolkien's Elvish (of which there are two different dialects...). I used some Sindarin Elvish in my TES fan fic, because I've spoken via email with some TES 'language experts', and they said the creators of TES never actual went through the trouble of making a full Elvish language. What little they do have in the games is partially inspired by Tolkien's Elvish languages, but it's not a full or real language. I say, why make up a new Elvish language when Tolkien already made it for all of us? It would be like making up your own version of French instead of using an already existing dialect. Silly, in my opinion. So, definitely go with Tolkien (of which there is Quenya and Sindarin). Hope this helps.