Don't you just love how when kids like something, they REALLY like it. There is no half-heartedness there, and I love how this comes across in their rooms. If they have a map, it will be a VERY big map,
Every possession is treasured and if they love books, it won't just be any bookshelf it'll be one with little tree animals on it (below Anzu fairytales card).
Their hobbies are immediately obvious the minute you enter the room.
And there is always a sense of adventure about them.
I think Wes Anderson perfectly captures this in his films particularly the Royal Tenenbaums. And in his films, it's not just the kid's rooms that go overboard on the hobbies!