Usually when I have an opinion it's based upon exposure and personal experience. Over the years in working with families I find it works best to give teenagers a bit of guidance with their rooms. Yes, definitely let them feel like it is their personal space and reflects their interests. However, guide them with the translation because it usually comes out better and they are happier. Plus, it's nice for a parent and child to collaborate on something such as putting a room together. I don't think saying " have at it" is the answer, again because I have experienced that this does not work well. A tween still needs a little leash, yes the leash gets longer as they get older. I have a teenager and you can imagine being a decorator mom, I have my opinions. We had a great time putting her room together. She chose colors, theme (she wanted Moroccan...I was so proud), she also did her own layout. I gave her two and three choices for everything, she chose from the narrowed down options. It came out great and we had a great moment when it was all done because we did it together. Anyway, just my two cents.