Peter Jackson based his elves on the descriptions Tolkien gave, as was only right. Tolkien based his elves directly on the elves in Nordic mythology - hence the "Scandinavian look" - but not slavishly.
All source material undergoes transformation as it passes through the artist. In Tolkien's case, he was a Conlang hobbyist long before the term was coined. He invented Elvish as an amusement; he then needed to invent Elves to be the people who used that language, and the stories to be the mythology and folklore told in that language, and the maps to be the countries inhabited by the people who told the stories. Since he was primarily writing for his own and his family's amusement, he was not consistent - see Christopher Tolkien's massive compilation of his father's papers for examples - and even when he wrote for publication, his vision evolved as he worked. Compare Elrond and Rivendell of *The Hobbit* to the same character and place of *Lord of the Rings.* It's a bit of a shock and requires some creative activity on the part of the reader to reconcile the two sets.
The cat just got settled in my lap and I'm not going to disturb her to go pull references for you, but again the public library will be helpful. Because of his popularity, Tolkien scholarship is readily available outside of academic venues, and his source criticism is among the most straightforward in the business, as he was an academic and talked and wrote freely about his sources.
Now, as for the aliens and movie templates - these templates are called "stereotypes." Lesser artists use these out of laziness and greater artists make creative use of them, explore them, and create new ones. The Little Grey Alien stereotype began with Betty and Barney Hill. Prior to that, the stereotypical alien was a Little Green Man. Barney recovered the gray image under hypnosis. I have seen, but do not have readily available to me, an analysis which convincingly connected the crucial hypnosis session with the first airing of "The Galaxy Being" episode of The Outer Limits TV show, which did not show a Grey per se but contained images which could easily be taken over and transformed by Barney Hill's creative process (assuming either that his abduction was primarily a psychological event and not a real, physical one, or that the process of trying to remember included creative work). The Little Grey Alien stereotype overcame the Little Green Man stereotype gradually over the decades, with its use in Steven Spielberg's *Close Encounters of the Third Kind* marking the point at which it achieved ascendancy in the public mind. Spielberg used variations on the grey alien theme in the climax of that film, and not one of them has not appeared in subsequent CE3/4 reports.
Digression - For those, like me, who believe based on the accounts that most CE 3/4 narratives are shaped by cultural expectations regardless of what really happened, it at first seems odd that the ET type alien (which makes its first appearance in Close Encounters) does not appear more in eyewitness accounts. However, the Little Greys of Close Encounters, the Hill Abduction, etc., are not perceived as distinct individuals, and ET is. Whatever phenomenon is fronted by the cultural concept of the Grey Alien, it involves groups, not persons.
Incidentally, the other alien stereotypes in current use - Reptiloids, Insectoids, and Nordics - as well as the Greys and the Little Green Men bear a strong resemblance to traditional Fey imagery. *Passport to Magonia,* by Jacques Vallee, is the seminal work collating resemblances between the fairy tradition and the ET tradition.
Goodness, what a lot of reading I'm directing you to! But it's all good and it's all interesting and it's especially fun to read this sort of thing while lolling in the summer sun eating potato chips and drinking the cold beverage of your choice.
