Perhaps you could put the big piece of artwork you have leaning on the ledge to the right? That might look nice.

I think a chandelier in place of one of those can lights would fill the space nicely.

Hang a painting or tapestry but keep in mind the sunlight will fade over time also a chandelier hanging would break up the space

Something 3 dimensional in metal or wood that is big enough to center on the landing wall.

The sunlight shining there breaks it up and I would leave it, at least for now. Instead, concentrate on gorgeous, colorful rugs!