Well, after some work on adding details I consider it as finished… The guitar. And the beginner guitar player’s room. 
I modelled the guitar after my own, but the room (or rather its corner…) is an improvisation.
This is my first serious Cycles-rendered scene (hope it looks good enough).
I’ve never owned a guitar, but that one looks huge. Other than that, looks pretty nice.
yeah scene looks nice, but scale is off…guitar and coke cans too big 
I’ve made a short animation showing the scene from different points of view.
Everything looks quite realistic. I did notice the scale being off but everything else is great! Did you use simulation with the cloth? It looks sweet.
Sure, the cloth is simulated. Had to bend and position it the right way before the simulation, though, to get the wrinkles right.
Yes, you have some troubles with the coke cans scale. Try pressing Ctrl + A and click on Scale to reset the scale size.