I adore the Cullens but there is much more background information on them than the Quileutes. So if Stephanie wrote a prequel to Twilight about anything, I would like it to be on La Push and through Jacob's perspective or something. I really enjoy being in his head, he is rather ridiculous and hilarious. Plus I just love all the characters from there. Seth and Embry... and Leah has a great story.
Again, I LOVE LOVE LOVE the Cullens, I don't really have any favorites when it comes to twilight, all the characters are so astounding. Edward's perspective was fantastic to read from, but he seems like a bit of a grouch before Bella comes along, the magic is reading from his perspective AFTER he falls for Bella, and I have heard each Cullen's history in some shape or form, and although some of them are less intricate than others, I feel like I know practically nothing about the how werewolves of Twilight lived before we are introduced to them. Not even Jacob! Maybe I have missed out on some stories, or am forgeting some parts of the book, but other than the fact Bella and Jacob played together when they were little, I don't know a single thing about his life before we meet him in Twilight.
So. In conclusion. Ha ha. It would be divine to get a prequel about the La Push Reservation!