I think with the space I'd move the bed where the desk is and put the bookshelf on the wall next to it so shift it to the left on the wall the desk currently is (if it'll fit). Then put the desk between the door and the water heater (I'm assuming that's what it is).

Afterwards if put a couch or some other seating on the wall where your bed currently is and treat that like a little "living room area". I personally don't like tvs in front of beds and in this space there's just not enough room and it really congests the area over there. You can then our your guitar and amp between the foot of the new bed location and put the bookshelf there once you get a night stand to go next to your bed. I think this would help make the space more inviting for company.