Good evening!
For the room design a sofa bed has been chosen. This sofa model is from Clei, and is called Kali Sofa 90-120. The most important caracteristic of this model, in addition to the horizontal design, is that in the night mode the space occupied by the bed is the same of the sofa during the day. This is really important becuse of the small dimensions of the room. You can buy this sofa online or you can ask to build it to a carpenter, in attachment I sent you a scheme of the parts and assembling mode. Above the sofa-bed I placed a library with the same dimensions of the bed. In this library you can place a projector and an HI-FI directly connected (not visibly) with the PC. The wall in front of the projector was designed white, like the ceiling for two reasons: to have a more contrasted image from the projector, and to increase the brightness of the room. In the area near the window, I placed a rounded desk with two chairs and the PC monitor. The floor remains the same and a big frame without glass is placed in front of the monitor, so that you can eventually choose a different character's poster to display in.
I hope that you like this solution, you can buy a projector for 50 euros from Amazon and a second-hand HI-FI for 100 euros.