I would most probably keep the design scheme neutral and functional especially if the gender was kept a mystery until the big day. I love the scheme above and the very decadent Jacobson Egg Chair. Its a scheme that's not to babyish,very sophisticated, calm and relaxing. Just what you need when you are up at 3am with a screaming baby!
I would even think about incorporating my love of all things vintage in there somewhere.
Thankfully my last little angel leaves for Uni in September so no worries about designing a nursery for me own use, but if any one else has one for me to do I'm there!