A milieu-based approach is good, but I think in order to keep things interesting, something needs to be done differently with the world, but that depends on what you would like to see out of this. Do you want the RP to be milieu-based with something along the lines of Gulliver's Travels or The Wizard of Oz where it's more about strangers in a new and unusual world trying to find their way back home, or something more Event-based like Lord of the Rings or Beowulf, where the story isn't so much about returning home as it is trying to solve a problem and crisis and these strangers have arrived at just the right time where they can make the most amount of impact? If it's more milieu, then we need to make the world strange, fantastical, and unusual so it's interesting to explore and people can be open to ideas with it. But if it's event-based, then that's not as necessary and more focus could be on the issue that's at hand.
I'm not too crazy about the stone collection thing. Maybe go for something else this time that needs to be done for the characters to go back home. Some kind of ritual, monster(s) to defeat, portal that needs to be opened, something along those lines. Or maybe it's something that needs to be discovered in time and people don't know right away, which would make logical sense. All the PMD games leave people pretty much in the dark right from the beginning, and only much later do they discover hidden truths and suddenly realize the whole story.
I like the idea of a personality quiz. It's about time a PMD RP actually does that. It dares people to try something out of their ordinary comfort zone and go for something new, which I think might enhance the experience. Plus having 2-3 choices will ensure that if choice #1 is definitely not what the person wants, they won't feel like quitting early.
I don't mind making a banner and world map though, but I just need to know a little more about what you plan on doing with this.
