You can put a rug in your room to make it cozier. A comforter with matching cushions on your bed will make your bed very comfortable. A bean bag can be put in to provide a very comfy extra seat.
Floor cushions can also be put besides your bookshelf so you can enjoy your reading. A wall hanging or a painting can be put on top of your bed. You can also paint on the wall above your bed with your favorite quote or any line from a song etc.
Your Christmas lights can be put to good use by being placed around your dressing table mirror.
You can put glass on top of your desk and place air tickets, letters, pictures or anything of value between the glass and the desk so your desk looks nice too.
You can blow up your family portrait and give a nostalgic vibe to your room.
A fine clock should also be put on either your desk or hung on the wall so you are never late. A hook bar can be put on the back of your door so you can hang your coats and scarves.