When it comes to fashion, black lit up by a dash of gold is always a winner.
So what about it in the garden?
I rather guess that one has to carefully balance out the proportions, since too big a splash of very dark flowers could result gloomy or simply dull, since most black blooms are sumptuous when looked up close but tend to fade in a border.
So here is an possible planting list:
Dahlia Arabian Nights and Black Jack (above)
www.thompson-morgan.com , www.bluestoneperennials.com