The dark cabinet in the corner is not working for the space. Too large to be considered a balance to the window. A mirror doesn't seem the right solution for this space.

I lowered the canvas on the opposite wall. Are you sure there is a better arrangement for the furnishings in this room?

It’s monochromatic but not exciting. Something with color needs to be added. Here are some different rug, which could prompt some colored pillows. These are from Wayfair.

There's nothing wrong with your area rug. If you implement these elements into your room you'll have texture and contrast that will complete the room.

I'd want just the sparkle of a mirror but not the image reflection

Agree with relocating the dark cabinet in the corner.

It seems like you are squishing the room’s furniture into the very center of the room between all the doorways into the room. The couch ends up partially in front of the window on the left. The doorway from the foyer into the room has an odd jog on the right side exposing a couple of the stairs to the 2nd floor. Have you considered making that doorway less wide (rectangular) to get rid of the jog? Then spread out the furniture a bit more, maybe in a different layout.

Some visual with mirror

Or may be narrowmirror with sconces on a side

or better with wall art

As for chairs above you can use