A gorgeous artificial olive, sansivera, find a gorgeous planter, or why stop at one. You could have two at different heights , there are narrow planters available for that purpose.

As Julie suggested or I notice that there is a power point on that wall so even a small side table with a lamp placed on it towards the corner, just guessing how wide that space is

I like the idea of the small side table with a lamp too. Otherwise I can never go past an olive tree. absolute favourite. Will look good anywhere.