Living Etc. has a great gallery of kids' rooms. Although many are gender-specific, some have a more neutral palette. Here is the link: http://www.livingetc.com/gallery/main.php?g2_itemId=109 Also, the Ruffalo house tour that was featured on Ohdeedoh is not overly gender-specific: http://www.ohdeedoh.com/ohdeedoh/slinks/the-ruffalo-home-on-dominoslinks-n-slingks-surreptitious-web-links-to-other-good-sites--074006

I have a six-year-old girl and a three-year-old boy in one room, too. Our house is older than yours, 1920s, so the furniture we chose is a little more cottage-y; a maple bunkbed and dresser and oak and pine bookcases. The colors we picked are a variation on the primary colors; pale yellow, slate blue, and red as an accent. We have these Ikea curtains: http://www.ikea.com/us/en/catalog/products/20124033 , but I've tried to stay away from too much Ikea stuff,, since it lends the room a "plucked from the catalog" look. I find that all types of wood grain tend to play well together, that it's pretty easy to keep colors unisex, and that if they each have their own bedding, they're pretty happy with the overall effect.

Now, if I could just borrow an extra dimension or a wormhole in which to store my daughter's book collection, everything would be perfect!