He may still be your baby, but he doesn't want to feel like one. Even if your tween son still loves rocket ships and trains, he's getting too old to have them plastered all over his walls and bedspreads. And the racecar bed is officially ready to be replaced with a twin or double.
That's not to say that you can't still have elements of his childhood as decorations. But it may be time to start collecting more sophisticated prints or replicas of antique engines to replace his Thomas the Tank collection.