1. Ancient Egypt: Ah, the wonders of the ancient world! My favorite ancient civilization to talk about, I would love to see more about the lives of the average person (farmer, merchant, craftsman, etc.) rather than always turning to Cleopatra or other princesses as a source of inspiration.
2. Non-European-based fantasy setting: Fantasy is really restricted to European influences in both setting, people, and culture, leaving plenty of perfectly good groups of people out. I would love to see more fantasy with African, Asian, Native American, and Aboriginal Australian inspiration. Nickelodeon did just that with Avatar: The Last Airbender and the result was fantastic!
3. Dystopian after a failed revolution: I'm getting really specific here, but I really want to see someone take a broken down society that's tried to change but failed. You can't win 'em all.
4. Adirondack Mountains: A beautiful setting that is a marvel of beautiful waterfalls, amazing flora and fauna, and small, hidden towns all along the way. Most of Adirondack-set books that I've come across focus on old murder mysteries set in the region and it's a little tiresome from a place that has so much more to offer.
5. Antarctica: Why not? The world's largest desert, meteorites, scientific facilities, and you'd be mistaken to think that everything is just ice all the time:
|Photo by Mike White , from Mental Floss website|