Ah, now I see the pictures. It is a tricky space, but I think you can get the drama you want. So many options will come your way from other readers.
A strong tactic would be to choose a rich wall color that you love. Right now you are tending toward a monochrome sepia tone in everything. Years ago, someone told me that a dark space can sometimes be made really dramatic by making it darker, and I've used that advice several times with wonderful results.
Over the years I've redeemed dark spaces with rich red, cobalt blue, emerald green, paprika, eggplant purple, deep rose, etc. Every house seems to have a hopelessly dark spot. The first brush-strokes of paint always make me gasp in horror at what I've chosen, but when done and the furnishing put back in place, the effect has always been deeply satisfying.
Textiles can be the hardest to find. Perhaps start with a fabric you love for the bench and choose a color from it for the wall. The bench is small, incidental, so don't be shy; choose something that makes your heart sing, and don't worry about it being too this or too that, or what others will think. This is for you!
Of course, lighting is important, both for safety in a stairwell and for enhancing the effect. I notice in your sample photo of a house you admire, there are black shades. These are extremely effective in enriching the whole effect, something you can do with chandeliers or table lamps or yes, even on wall sconces.
Take your time, picture all sorts of options, and then plunge in. It's mostly just a can of paint and a single day of painting. And, if you don't like it, it is just a single day to paint over it with a new color (which I confess I've done a few times on the way to getting a color right).
Best wishes for coming up with something you love, and I hope this message is followed by lots of creative ideas from others. :-)
Q