nothing.

I agree nothing should go there

If possible I would consider extending the closet walls up to the ceiling down the line.

It's a trend that passed but the homes built for their purpose are still around. The best displays I saw back in the day were family pieces, a cradle, a trunk that came with grandma when she crossed... I think the trend died when people realized keeping the spider webs and dust off was too much. Still as long as there's a flat surface the temptation to fill it is there....