Hi S, mirrors are effective when they are reflecting something visually interesting, like the view from an opposite window to the outdoors, or when used to create the illusion of additional space. The mirror in this picture does neither of those things. With the TV removed from the corner, there is more room for the window treatments to fill the corner properly (right now they look a bit squished), and it would be fine to leave it bare, or put a low accessory item in the corner, like a sculpture or a potted tree (not too tall!).

As for the rug and table, there are 3 ways you can go: since the striped wallpaper and the floors are so neutral already, you can afford to add some color into the room with the rug. With a colorful or patterned rug, a clear glass table top would be good, because it allows you to see the rug. In that instance, the rug becomes the focal point of your furniture group. If you want to keep the rug very neutral too, then a solid table top is good (in an interesting material- maybe wood or stone). In that case, the table becomes the focal point of your furniture group. Lastly, if you want a neutral rug and a transparent table top, I would be sure to add some color or pattern to your seating- either the sofas themselves or throw pillows on the sofas, to inject some energy and keep the whole room from feeling too bland.