Measure twice, buy once. Items may look smaller in a store than they do when you get it home. I personally measure both the area where the item is going in the room, as well as the size of the item at the store. I know this seems like overkill. When you get home, things may look a lot different. You may want to have more control over that process. Do your entire planning first. If you are going to spend more than a few hours in the chair, make sure to get an ergonomic one. Try out the ones at Staples for example. Your back and your backside will thank you. Lighting may seem like an afterthought. Some people get that last, however, lighting has a lot to do with the atmosphere in the room. Educate yourself about lighting. I personally don't like ceiling lighting unless it's in a dining room or kitchen. Ceiling lights may look like you are in a hospital or doctors office. You may want to avoid that! Make sure to get task lighting for the desk. The layout you have is fine. Keep in mind that 2-3 feet is recommended between chair and bed in this room. If you will be using this room a lot, bumping into furniture will get old quickly. Again, planning is crucial. Keep in mind the wall color and potential art on the walls. Don't get something just to fill up the space. If you do plan on getting art, take your time and get pieces you love.

Paint the wall color the same as your furniture color. It will all blend together and make the room feel larger. What are you placing on the bookshelves? Books or decor? If books, measure how many linear inches of books you have and do not purchase more bookshelves than needed.

Do you need a desk with storage? If not, I'd look to get made a wall hung desk that extends the full width of the room. It would be a tidier, sleeker look.