mustard or sage is not the first colors that come to mind with a brown leather sofa.

a dark olive green, a dark gray or even blue would compliment the Brown leather.

It's a realatively small space, you could use the mustard in accents. Will you get an area rug?

https://rugs.com/brown-10x11-amina-area-rug-6251296?gad_source=1&gad_campaignid=22923419515&gbraid=0AAAAAC-j9AuA9rKOv137YqeHMWgNW_vVx&gclid=EAIaIQobChMI6vnxj_mblgMVfDQIBR3gVwAKEAQYBiABEgLEsfD_BwE

I will definitely be adding a rug! I hadn’t thought of blue but just saw a post about it.

Funny, sage is the first color I think of when pairing with a brown leather sofa ( which is a classic color for a leather sofa ) . Neutrals would work, but since you like color either greens or blues. Be sure to bring samples in to try in your space, lighting, furniture, etc.

Go for the (mustard) gold.

(Btw, no furry friends were harmed to create this visual. The throw on chair is a faux fur.)

When you have a brown leather sofa, think about colors in nature - especially for accent colors.

I agree with Lyn above - I forgot to pull a dark gray photo!

Personally, this blue is not something I would use - however, it is a popular color:

Olive Green - I think darker would even look better:

BM Hale Navy was the color of the year several years ago - I still see rooms where people are using it now.

If you want to throw in mustard yellow (+ some other pop of color) - SW Alabaster might looks nice:

SW Evergreen Fog was also the "color of the year" a few years ago:

If you want to try something bold!

There are many greens that will work with the brown leather that you have:

Choose your rug and art work first then decide on wall color. I have an Ideabook called "Brown and Black Sofa Dilemma" because the subject cae up so often. Definitely a rug choice needs to be made to balance all the large brown pieces in your room beside the sofa: armchair, coffee table, side tables, dark brown floor. You need a contrasting rug and art work. I personally like white in a room with many dark pieces, but maybe you're going for a moodier feeling. What feeling are you going for?

Not suggesting this rug particularly, but it's an example of how to balance a dark visual field like a sofa with high contrast rug, coffee table, large sofa pillow, white curtains.

Living Room Shot 3 · More Info

Note boldly patterned rugs, light armchairs, light art work. However, floor is blond.

Living Room · More Info

A Family Friendly Living Room in Devon · More Info

Pairings of art and rugs:

Ascella Canvas Art · More Info

Diamond Illusion Multi Rug, 5'x8' · More Info

Art Painting, Black/White · More Info

Impressions Light Blue, Pale Cyan Rug, 5.25'x7.25' · More Info

You may find that developing a whole-house color scheme will be both satisfying and economically sound. Your color scheme should be personal preference, not what is trendy. In developing a whole-house color scheme I would love forever, I was helped significantly by this article and the ones embedded in it from the same author: https://www.fromhousetohome.com/whole-house-color-scheme/
Your sofas appear in the photo to be a warm muddy orange brown, but I know from experience that photos can lie. Still, if they are an orange brown, I love combining that color with olive green and blues to wines in accent. You said you will add plants so you are already adding green. And I agree with other posts here regarding adding blues and greens. @dani_m08 gave you lots of photos to consider. Can you line up some of your art along the wall to show us your style and the colors in your art?
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Your ceilings look low like mine. I learned to paint the floorboards, crown molding and window trim the same as the wall to help the room feel less squat.
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I also learned that art looks better on dark walls than on light walls. TVs look less in-your-face on dark walls. Views outside windows are more noticeable when walls are dark, and when outside views are more noticeable, that makes your space feel more expensive and interesting. Another thing I found with short ceilings is the power of uplighting, especially if reflected off a lighter ceiling. I am attaching photos of unfinished bedrooms in my house. The one with the ceiling fan shows how uplighting is lifting and I like the effect of bouncing light off the ceiling. The walls are SW Rock Bottom, a chameleon I am in love with for my cocoa brown cork floors. The ceiling is SW Evening Shadow, a lovely grey that reminds me of November skies. The other room uses the same SW Rock Bottom on the walls with SW Daydream on the ceiling as my touch of purple. You see how the SW Rock Bottom is a chameleon. The room with the fan is a south room; the other room is a north room. I'm not saying you should use SW Rock Bottom; I'm just giving you examples of real rooms with dark walls in case you are interested. In the photos, my floors look more orange brown and lighter than reality. They are a dark chocolate. Lighting is key in rooms with dark walls. I embraced dark walls because I love the new sculptural light fixtures available now. I have attached a couple examples, because the ones in the bedroom with the ceiling fan are more traditional for my husband. I love your lights, by the way. The stringers on the stairs will match the walls when painted. In case you are wondering about the dark blue, it's SW Charcoal Blue, another chameleon that can appear as a dark teal to a dark periwinkle. I hope these examples help you in case you are considering dark wall colors. There aren't a lot of good examples out there.

Primary bedroom · More Info

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workout room · More Info

workout room · More Info

Upstairs renovation - hallway and shallow storage · More Info

stained and with top coat but not painted yet · More Info

Blue?

I also aligned the chair on the left with the sofa, so they read as one divided-seat unit. For me, that looks more intentional than the slight angle does.

etsy rug