There are tons of papers available that would go with your midcentury home. Many people tire of a paper quicker than they are ready to redecorate and they can also look dated in a couple of years. Metallic papers were big im midcentury...perhaps a metallic silver paper? Are you also considering paint? You can get it in so many textures and a blue wall to match the blue in your loveseat would be lovely with some midcentury art and sculpture, or photographs on it. A mirrored wall with or without art or sculpture would also work with midcentury. These treatments are easier to adapt should you wish to change the look slightly from time to time. I would suggest replacing your stairrail with chrome or acrylic if that is in the budget...see how well the loveseat frame looks with the fabric? I hope you will post the "after" photos for us to see. Above all, enjoy the process!

Should have added, this is the existing layout:

Thank you for your comments. I really appreciate your help. I think we are on the same track. The rugs I have brought home have fought with the terracotta colour plus the busyness of the small tiles. I did come across this picture on Houzz, which I think looks good. What do you think? It would need some of that burnt orange from the chair upholstery as well as the aubergine to tie in but I liked the dark border line, it matched with the grout.

I think you are wasting money . I'd leave the columns , do a couple of bi-fold aluminium doors , do a nice leather corner suite , and artwork , a Tv , make it more livable . I'd do a glass balustrade on the small stairs , 3 or 4 creeper type potplants and a couple of 'objects d'art' along the solid balustrade . Do you have another dining room ? If yes , make part of this an office/study ; if no , then a nice table and chairs . Right now , it looks unloved -- make it easier to fall in love with it , and you will !