@Veltra Mansions will not have walls which are only one tile high. If you try and put objects in there - even a basic wall cupboard - they are going to be taller than the walls. It will also mean that the head of the sprite is scraping the ceiling the whole time. So first off, change that.
Then consider what you are doing with your ceiling tile, particularly at the top. You have it solid, rather than giving the impression of being a wall. Yet if it is a lobby, that is an outside wall. The ceiling cannot stretch back that far, this is a mansion, not an underground room. So that would be the next thing to change. Assuming that it is indeed an outside wall, then you will need windows of a suitably grand style.
Here is an example of what I mean. I've done it quickly with the snipping tool instead of taking a proper screen shot, so it's a bit blurred. You will see that the walls of the room are clearly indicated. But the room itself is still smaller than the screen. That is not a problem which needs to be solved in the way that you have.
This is a rather grand mansion, so there is plenty of 'empty' space. However, it is broken up by having a more interesting floor tile than the plain wood floor you have chosen. Remember you can give visual interest by doing that, rather than having to do it always by putting objects. The example given also in part answers your question about what objects to put in.