I can't tell you too much about the composition of the room, since this would depend on what puzzles you want there to be and which objects you need to have in there. But I actually quite like the Sketch you did. In fact, I would not try to redo it "nicer" with straight lines and correct perspective and so on, I'd prefer to keep it as it is and just do a nice lighting and coloration, which might look very good. Only thing I'd do is add some more details. no more big Objects, just small stuff that makes the scene look more alive. Maybe a vase, some bottles or a mirror on the sideboard, a piece of cloth on the table, maybe with a wooden board with a bread and knife on it, hang some garlick or dried chilies from the beam in the foreground, add some contours to the furniture and maybe visible hinges, cobwebs here and there, nail a horesshoe above the entrance door, have the barrel on the right open and show the content, a mousehole, some stuff forgotten on the big wardrobe, just to name some suggestions. Will you colorate by hand?