@Yog: Well, we'll be sticking to the books, but our characters will be the 'main' characters and the RP will focus on their own adventures. Basically, we're writing from a normal student's perspective, but there will be lots of references to the Golden Trio and stuff because of all the trouble they're up to. Also, like Aiisen said, Slytherins aren't evil. Here are some clips about them from the Sorting Hat songs...

[i]Or perhaps in Slytherin
You'll make your real friends,
Those cunning folks use any means
To achieve their ends.

And power-hungry Slytherin
Loved those of great ambition.

For instance, Slytherin
Took only pure-blood wizards
Of great cunning just like him.[/i]

And besides, the S.H. remarked in the second book that Harry most likely would have 'done better had he been in Slytherin'.