If you want to highlight the staircase wall then your could use earthy colours such as a yellow ochre! The wall could be enhanced even more by using suitable frames and making a good collage composition for all the photos that you have (I can see many lying on the dining table). This colour would match well with wooden furnitures

Reclaimed wood ,use pallets you could take apart and nail them up .Could be free if you look on Craig's list for free pallets

Give search for home theatre door in houzz and it will give you a few ideas. But finally what you have to think or take help from interior designer is about the theme of your home as this door should also get aligned with your house theme. In general having hallway as part of home theatre is not advised so if you can change it, it would be better. But if you can't then at least install auto closure.

Gazzala, You are taking a very wide shot. Without the pics and relative dimensions it's not feasible to give you any meaningful suggestion. Style Spa pieces are usually particle board furniture and it is not suggested to move them often. Your husband seems to suggest for the same reason. Thanks, Nitin Cornerstone Designs, Bangalore.