If you're intersted into doing more you can always check out interior magazines or websites. There's a lot of really cool ideas for layouts and prop design to found in those.
Another idea is to imagine how would you decorate and arrange this place if you were living there. Like, if you like to read, putting in a cabinet with books, a cozy chair and a lamp for when it's dark could be cool. Or if you'Re the kind of person who likes hanging stuff their wall, just add some of that to your drawing. Or you can also do the same by creating a character in your head and go through the same process, but from the perspective of that character instead of yours.
But as @PeterH mentionned, you also don't necessarely always need to fill the whole place either. I think it already works well as it is overall.
As for the shading, I think you just need to push the darks a little bit more to create a better contrast. Something a little bit like this maybe?
A lot of what I did was darkening the areas where objects meet (like where walls corner and where the furniture touch the ground). I think it's called occlusion, but don't quote me on that. I also darkened the closer planes facing us as the light from the window wouldn't affect them as much.
But otherwise, I'd say good job! That's a pretty good perspective job