I was a teen through the 90's. My room was a reflection of me. Whatever mood I was in you could find something in my room to represent me. My older kids, now adults, decorated their rooms the same. My now teen kids no different even with the this awful social media crap. I encourage all my kids to express themselves through their personal space because that is real and the crap on social media is false. It also gives me insight into their head. Know their interests, spark conversations, ensure they know they are individuals and not suppose to be like everyone else, and helps them understand people can change interests throughout their time. My mom knew me from me expressing myself decoratively and I think that is one of the best ways a parent can understand their kids.