Some people, as shown in the examples, have opted for a plant or something simple. I think here less is definitely more. The more you fill it with, the more it will be a focal point. It looks as though your downstairs foyer is a different color than the upper level. I would paint them the same color, as to make this space less notable. Best of luck!

I had the same landing in my last home and I decorated it very plainly..added a large mirror and some pottery. Pic below does not reflect your landing, but it gives you an idea of the look.

Thanks for both your ideas. I used to have a potted plant on that spot and nothing else. My front door used to be a glass one but I had it painted mahogany and blocked all the natural light on that spot and plant didn't survive. The reason I painted the glass door was that my neighbour's big tree was casting eerie shadows at night. LOL I got scared at night.

Back to the issue, I'm not keen on fake plants.

Should I try to fill that whole wall with picture frames?

Also, the top walls will be painted the same gray as the lower wall. I'm waiting for hubby to do it in the summer.

a peace lily would do well there...

and I think a mirror (reflecting the plant) would be lovely. the small objects (pictures and frames) detract from the beauty of the staircase, in my opinion.