Your little boy’s room is his own private space. It is his own world where he can let his imagination roam free and he can immerse himself in his fantasies. This room is by far the most important possession he has at this point in his life, so you are going to have to treat it that way when you begin to think about setting it up and decorating it.
Giving a grown up look for your little boy’s room will surely excite him. He will feel much more confident when he feels that you think he is “grown up”. He will also appreciate the “grown up” items that he will get to have for his room.
For starters, give the room an overall feel of maturity by sticking to more subdued color shades over the bright and overly light ones. The bright primary colors that are very common in children’s rooms would not make a good base for the “grown up” atmosphere that you want the room to have. Furthermore, real grown up men like their colors to be a little more muted than that of the women; thus, it would be a safe bet that your little boy would prefer it too. Be careful though not to make the room too dark because this would take out the fun character of the room. After all, this is still a little boy’s room. To prevent this, choose the main shade from the lighter “manly” colors like tan or brown. You can also place light color themed posters or wall tattoos around the room to make it feel a bit livelier.