How would you recognize your kid's (or kids') room(s)?

Just arrived in a strange city and came alone to my son’s new apartment. He told me which room is his, but I would have recognized it instantly. Two iPhones, sunscreen and medicines in a fanatically neat row, books, four laptops and an iPad. Typing this on his Mac. “As if I didn’t know him, as if I didn’t know my only kid. As if I didn’t know the way he brushes his hair off his forehead.” (Paul Simon) What “tells” would identify your kid’s place to you anywhere in the world?