Do you plan on keeping the leather sofa? replacing armchairs? replacing area rug? more details will give you more valuable suggestions...

I plan on keeping the single white chair but everything else is open for change

Why the change? Does the furniture have to be dog friendly?

What about another white chair for starters?

I would get another white chair to match the one you have or something similar?

Replace your area rug and pick something you love. Pick a color from the area rug, for your Sofa color.

Move the two white chairs and place them where the two gray chairs are. I really don't think you need more seating or do you? If you do, just replace the gray ones you have with two patterned chairs, that have a little white in them. Be mindful when you pick the pattern. Make sure it doesn't fight with your area rug.

Move the tv to the middle of the wall and move the shelving unit to another room. Less is more on this wall. The tv on the console is all you need on that wall.

The fireplace has too many items, on it. I would remove the framed black art and move the small white art in it's place. Remove the plant.

I like your coffee table. So keep that. :-)

Saw this in your idea Book...... Love the colors. Great inspiration picture.

Cape Cod Renovation · More Info

My suggestion is to bring more contrats into the room. Here are my suggestions with keeping your leather sofa, white armchair, coffee table, chair side tables (round ones). A vintage rug with a lighter background (shown is a Ruggable, goes to washer/dryer), 2 black armchairs (to replace the gray ones), a rattan ottoman, a console table behind the sofa with lamps (you can run extensions under the rug), a reading lamp next to white chair, and side drapes with black rods on the windows for more warmth to the room with texture. I've added a level of lighting with lamps. Then complete with accent pillows and more colourful art on the walls that coordinate with your colour scheme such as illustrated below.

I also suggest a more substantial black pendant over your dining table.

Thank you for the specific suggestions. This is very helpful.