The paintings

OMG you have that beautiful window nook and no seating there? And the tall cat tree is blocking the window on the left.

Move the chair next to the TV into the window area (at an angle) and move the tall cat tree next to that column it its place. A short stack of books and a coaster on that table in the nook so it's usable when you're sitting there. And a lamp or floor lamp.

See how the light reflects off of those columns? I would put a vertical gallery of mirrors facing each other on each of those columns where the light is. The same distance as the window frames. The mirror in the hall reflects the windows but needs to be mounted on the wall.

Get colorful throws and pillow covers in your green, gold, black and white.

These are on Etsy.

If you did not have a cat I would say to get a marvelous Oriental rug and then get pillows and art that picks up on those colors.

But do not ever sink money into an expensive rug with a cat!

So here's what I would do.

Spend some time together looking online at some art websites like Saatchi, minted, great big canvas and see what you two can agree on.

Ideally somethings with color.

Your place is rather bland now.

Then buy some art for your place.

Also, your mirror in the entryway is hung too low, and is sideways.

Actually, it is a bit boring.

Please keep your eyes open for something more exciting.

Once you get your art, then you can replace your sofa cushions to coordinate with your art.

And you can decide if you want to replace your rug.

I would add some live plants to the other end of your room.

Get a live philodendron or pothos with lots of hanging leaves to sit on top of your bookshelf and cascade over the side.

Also, the three plants in rope hangers with no leaves - unless they are something you just planted from seed or seedlings, please get rid of them and get something bushy and/or trailing to put there. Tradescantia is a good idea, there are many species. Also swedish ivy. They are both great hanging house plants, easy to grow and propagate and don't need a lot of light, and of course, philodendron and pothos.

"Then buy some art for your place."

"I would add some live plants to the other end of your room."

They do have plants and they did buy art and are asking how to incorporate the room with it.

I agree with the rug. It's fine. You can add plenty pops of interest to go with your art easily enough through accessories.

I don't see anything wrong with your empty pots, any plant person knows that tending plants requires replacing them occasionally. The ones you have out are healthy.

Maybe sheers in the window that let in light but add a little privacy.

Somthing similar to these trays are retro MCM in your colors for over the TV, or sofa it you switch them use some with black as suggested.

On Etsy:

Get somethings in white and mcm for the bookcase that will pop and add interest.

As a fellow cat lover, your place has to be comfortable for the kitties! I would move their cat tower into the corner, to the right of the tv. That placement sort of balances with the floor lamp on the other side of the room. Then I'd reorganize the area in front of the windows to make sure the kitties still have an outside view. Whatever you can do to visually widen the area in front of the windows will help the overall proportion of the room. For example, continuous shelving below the window, with artful placement of plants and decorative (non-breakable) objects. I love hanging plants, but not if it causes the drapery rod to bend, as it is currently.

btw, are those door openings on either side of the windows? Or is there a third window on the left? And is that a coat rack to the right of the sofa?

The black bookcases could benefit from some light colored objects, as tracefloyd suggested. Possibly you could use stocking hangers, or something similar, to hang some artwork in front of the books, if the books are not frequently accessed. I'd consider some decorative lighting on top of the bookcase - perhaps a vintage tv lamp, or something with character. I absolutely love lamps and lighting, and think they're a great way to add personality to your room.

The pillows that tracefloyd suggested are very much the direction I would go. You want to combine your soft, earthy colors with bolder black to harmonize. The existing pillows read as pastel with all the black in the room. I could also see just off-white or gray/black pillows if they have lots of texture.

Crude mock-up of moving cat tree:

More pillow ideas (hoping they don't show up as gigantic photos!)

Forgot to add: I like the area rug, in part because it is close in color to the sofa, so it expands the room more than a contrasting rug would.