I beg you: do NOT put wood paneling on the walls. I take it you are not in the US, nor are you familiar with ranch style homes of the 1950's. That being said, I'll move on to other options and suggestions. Let's look at the 3 functional areas you have laid out separately and then how to bring them together as a whole. You have an office area, entertainment area and a sitting/living room area. For the entertainment area (the wall with the door): *I took a look at Ikea Stockholm collection available in the US which may not reflect finishes that are available in other countries. There appears to be a low TV unit available (see image below) that may work nicely to give this wall visual unity and height. (Use the same finish as the units in the office space.) Is it possible to mount your TV on the wall? This will give you height. And the unit will give needed space for your receiver, record player, etc. It will also give you storage space. Your office area: *I would suggest a black top but keeping the chrome base legs. The chrome base would complement the chrome legs of the chairs. (That is, it looks like the legs are chrome color.) I still suggest a gallery of pictures for the wall. Or if you need shelving, use no more than 3 floating shelves. Ikea has these. I had bought 3 myself last year and they are very nice. If you go with the shelves, buy white. (I explain later.) The sitting room area: *This is where the area rug should go, large enough to expand to under the front legs of the sofa. Look for something that has texture, such as a shag or rather something that has pile--not a smooth surface like the wood floors. I looked at the Stockholm sofas. They are beautiful. For accent and a finishing touch, you may want to add some decorative pillows. The coffee table is lovely and hopefully it has a black top with the chrome base, as it appears. This reiterates and complements the table in the office space (pulling the 2 spaces together visually). Bringing it all together is done with colors. For the walls. Go bold with white walls and contrast it with one accent dark wall. Since you are interested in a serious color, go with a dark chocolate accent wall behind the sofa. Check to be sure that the dark chocolate compliments the cabinet and wood floor finishes. Why paint the other walls white? So that you will have contrast with your cabinets and it will make the dark wall even more dramatic--and serious. Look for a rug that is lighter than the wood floors. If you want pattern, try to find one that has the colors in your sofa, some white and some brown. This next suggestion may sound really strange. Trust me, it works. Go into your closet and look at the colors in your wardrobe. The dominating colors are what you love most. If the colors I have suggested work, pull out the pieces in your wardrobe that has these colors. Lay them out and see if you like the combination. If not, pick out the 3 pieces you love & repeat until you find a combination that works for you. Whatever you do, look at least for some contrast. It is possible to have a monochromatic and other color schemes but this requires more experience with colors. As I said above and I agree with m_madd, you have a great layout. Design it to be clutter free. *By "flat" I mean the colors as they appear in the layout above are without contrast as a whole, lacks visual interest as a whole. Color plays a major role in how we feel, even think and act. Use it to make yourself feel good. Here's the TV unit.

An update for y’all: So, I wasn’t quite ready to pull the trigger on painting the entire room blue, but I did go ahead and have custom bookshelves built and installed, in the same shade of blue. I figured I could paint the rest of the room afterwards, if I wanted to. Here’s that wall, just finished — I’m elated. The shelves are fully adjustable, so I can remove one if I want to hang a piece of artwork there. I purposely did not want any drawers or cabinets, just shelves.

My wife has worked home for many years and we’ve just finished renovating a bedroom in a 70’s house into a home office. What you might think about in your situation is that two significant considerations for her that went into the office planning process were: Lighting; IMO, few homes have adequate lighting for extended periods at a desk in a home office setting, particularly for middle aged eyes. She works from a larger desk now than she needed when she did her school homework. Additionally, effective video chats have less distractions when the subject and background are well lit with few shadows. Our goal was multiple light sources to try and imitate a TV studio to flood the desk and surrounding area in light. The better lighting has resulted in a lot less fatigue and eye strain. Electrical outlets; modern homes are better supplied, but older homes often have too few outlets for the electrical demands of a modem office. Computer, monitor, printer, desk lighting for video calls, phone charging, WiFi hubs, etc., all meant some additional outlets for us otherwise we’d have cords everywhere. My goal was to put electrical outlets near the electrical loads to minimize cord runs and trip hazards. The wife has her sewing machine, sewing table and fabric layups in the office as well as a small table and chairs that our son will take back with him “one day”, so the room is cluttered. It doesn’t really matter. Just so long as it’s neat in the background for her conference calls. The electrical upgrades have been wonderful. It’s worked for her.

Take advantage of the wall and build in storage and a continuous counter for two chairs. t