I should mention that I'm going to be selling the house. My wife has passed and I need the money for my 3 year adventure in Europe. That photo is a few years old. We were happy to have a place to sit. But, I agree, it was hideous, lol. I've picked up some better furniture at Habitat for Humanity. The art is near the ceiling because that's what you see when you come down the stairs or up from the family room. Its kind of a focal point. And I like it from the angle below. The image of God reaching down and Adam reaching up seemed to tie in with the two stairways of the split level ranch. But, again, I'm painting to sell the place now. So, now, I'm just thinking about tying the living room paint colors into the existing color scheme. So that's one vote for changing colors. Do you have a particular shade of green in mind?

What a beautiful space! I don't see your living area as needing to be updated, as it all seems to complement and flow well. I love the rustic elements. If anything, I would consider painting the built ins the same as the kitchen cabinets, or perhaps a shade darker. I think the mantel is perfect.

OK...oil based poly STINKS for WEEKS afterwards. And it turns the 'orange yellow' you are describing. And it will turn ANY COLOUR you choose to an orange tone. If you like the idea of the finish off-gassing for 30+ days while you try to find a place for yourself and kids and dog to live, you are welcome to go with it. I'm not a fan of oil based. The VOC contents are ASTRONOMICAL (880 g/L in one of them...compare that to the CARB requirement of LESS THAN 175 g/L in California). Many of these finishes are illegal in California and the 11 states that have adopted the CARB II indoor air quality requirements. It is a myth that oil based finishes are TOUGHER than water based. Polyurethane is polyurethane is polyurethane. The issue is when you go for the same PRICE TAG as the oil based finishes. A low-priced oil based finish (that has been on the market since the 60s without so much as a PRINTING up date on the can let alone a recipe change) is DIRT CHEAP. Why? Because those companies made their money DECADES AGO. Now they are just enjoying the HORDES of money from the investment they made in the 1950s (nope...not kidding). If you get a 'dirt cheap' (aka DIY level product from Home Depot!!!) water borne poly you will get what you paid for = a DIY level finish that is not as tough as the toxic stuff from the 60's. The TRICK is to work with HIGH PRICED water based finishes. The stuff that comes in 2 part products (call the finish and the hardener/catalyst). They carry big names like Bona or Loba. They carry high price tags (like double or triple the cost of the toxic stuff). They also carry VERY IMPRESSIVE wearability. The big boys from the big boys (Bona Traffic HD or Loba 2K Supra AT) are the toughest finishes outside of a factory. They are MAGNIFICENT. The PROFESSIONALS that work these finishes are the best of the best as well (or should be...some hammer swinging 'guys' give it a go once in a while and it shows...). And those people are not CHEAP. Why? Because they took the time out of the schedules and money out of their own pockets to attend the 3-5 day training courses for these finishes. Only the DEDICATED do that. Everyone else just looks it up on Youtube. My quest to you is: How happy would you be to find the house unlivable for as many as 30 days because of the stench? Are you a migraine sufferer? Do you get nose bleeds? How about your kids? Does anyone in your family have 'sensitivities', allergies, asthma, COPD, etc? If anyone has any of these things I've listed, then oil based is out. I've seen people get nose bleeds from sleeping in a home with freshly finished floors with oil based poly. Some vomit. Most have BLINDING headaches. Migraine sufferers can't go further than the front steps...the smell stopping them from entering the house. Just because it says 'can be walked on' in 1 day and furniture back in 5 days...doesn't mean the SMELL is gone.

You might want to look up early 1900s color schemes from the Arts&Crafts movement - aka Craftsman or Mission style (sorta).C... just for inspiration, you wouldnt have to go full-blown A&C in your decor or anything. What you have in mind sounds very sympatico. Those styles all were a reaction from the stuffy fussy Victorian era, and emphasized natural materials like stone and wood and took inspiration from colors from nature. You know - you do have quite a nice color scheme already picked for you in your stone work. Do you like that stone? Im seeing some nice blue grays, browns, gold-browns and the mortar beige of course.