Decorating a shared nursery/adult bedroom? My baby is due contained by September and I want to...

My baby is due contained by September and I want to start a nursery for him/her. I don't know what it is,so it needs to be unisex. My solitary issue is, is that for the time being until the newborn gets rather older/my sister moves out, my bedroom needs to function as both. Any design for designs that can sort of turn my bedroom into a welcoming place for babe, yet still function as an mature bedroom? I'm thinking of painting the walls a soft washed out, but I'm pretty stuck after that one.
Answers:    I like the wan as an idea for the wall color, and if it is a girl later you could use a "spring-like" theme, using butterflies, flowers etc which could also work for an full-grown. If it is a boy maybe you could do a shore theme, but I don't really own any good accepted wisdom for a boy.
I would go next to a nuetral color and decorate it fittingly, like prictures, rugs, bedspread and that way you can fine-tuning it as necessary.