You can foreshorten the hall with a striped rug. Add bright colors like this and who'll care about how long it is? The unity of the black frames might make for a great gallery grouping. Cut out the shapes of all your pictures in butcher paper and lay them out on the floor to plan a grouping. Then tape the to the wall where you want them to see how they'll feel. If the grouping is the right size, you might mount a floating shelf under them. That will keep the floor clear but will anchor the decor wall.

paint the end door a striking colour, horizontal stripes on the ceiling, and 3 large pendant lights. not sure how adventurous you are, but you could consider painting different colour "zones"- 3 different colurs as you walk down the passage.....possibly even 3 short carpet runners. i love the idea of wainscoting-but you will lose precious centimetres. You can get paintable wallpaper wainscotting.

chookchook2, thank you, I was having an anxiety attack thinking I was about to make a horrible mistake both visually and financially, my builders who were hanging the doors said they were going against everything by hanging them with the shorter panels at the top, (upside down) M.M didn't want to get involved and frankly couldn't see a difference? neither could my daughter? I have an older Queenslander home and the doors were already being cut down to a non standard size, I thought this made them more obvious, like hobbits were living here? I had to post on FB to get another opinion as well because he was going to charge me by the hour and the cost of 3 new doors, but he managed to flip them over and trim them again to fit. I am so glad I stayed to keep an eye on things, otherwise right now I would be terribly disappointed. I still can't upload the finished pics?

Some good advice above. Centering a single, large artwork over your couch and adding tall lamps / greenery in the corner is the way to go. But there are no rules with art, and a piece that spans the full width of your sofa, especially in your space, will work much better than one that doesn't. The artwork itself is a very personal choice, but look for a piece that augments your scheme. Ours can be colour customised as you wish - this one could be a good starting point if it resonates with you