I found my inspiration in a lot of different places. This messageboard had probably the biggest influence in that I got a lot of my ideas from here. I also got some ideas from the Wizards board and the Feywild excerpt from the Manual of the Planes that went on the
WoTC website a while ago. I also found a lot of really cool ideas from a Dragon Magazine article about the Eladrin city of Mithrendein and a Dungeon magazine adventure called "Dark Hearrt of Mithrendein."
The part that really made the adventure work though was finally putting to use advice I've been reading about for years. When talking about running outdoor adventures the advice is almost always run them as a big dungeon. Well I could never figure out just how to make that work before but I did it this time to great effect. Having the players march for a few days only to come to some decision point really made the session move while still recreating the sense of travel across a strange and alien landscape.
Of course it helps that
4e is easy to design encounters for. That gives you a lot of time to devote to making the adventures more memorable.