I found these on Houzz

You'll get plenty of fabulous ideas when you type "under stair storage" in the search box.

I don't want under stair storage, I am looking for decoration.

The built-in wood design of the adjacent cabinet is clean and modern. So as not to waste the under stair space and not interrupt the clean spare look, I would put in a blind door that matched the zig zag of the stair, with barely visible hinge hardware on the left side (probably will need at least two and maybe three hinged doors), then matching the exact stain and wood, create a blank slate look, flush with the cabinet and wall trim. And, there, hang a piece of artwork, or wall sculpture. Keep in mind, when you do this, the white of the zig zag stair will pop, but I don't think that's a bad thing.

I found the following in houzz. Your panel colors could either be white or that of your wall unit.
http://houzz.com/photos/1894115

Yes, Heidi, great example of what I was referring to, though it would be flush with existing cabinet. I still recommend the wood, because otherwise the double zig zag would be too jarring visually. And the way the wood is detailed now, all wood would punch out the stair nicely, as what it is.