We had the twins in our bedroom until they were 9mths old - then DD got moved from the bigger bedroom into our smaller spare room and the boys then into the bigger room.

We never decorated the bigger room until we knew who was going to end up in it - ie: If we had 2 more girls or g/b twins then the twins would have used the bigger room until we would have put all girls in together. Saying that we now only have floor rugs and wall stickers as "gender' decoration which is pretty easy to do when you decide the room situation, everything else was pretty gender nautral and more in keeping with the colour scheme of the house IYKWIM.