I have been having the same problems for my black feral which I have adopted. I thought of Midnight, Merlot (dark and soft like the wine), and finally settled on Merlin ( I know he was a wizard, but not a bad one). I have two black females (one lives with my mother in England now) called Cinders and Ellie.
We've had several black cats and names have included -
Morgan Le Fey
Dahlia (as in "The Black Dahlia")
Minx (bro to Jinx and one of my "soul mate" cats)
Meschach, Shadrach, and Abednego (all littermates)
I've had a pair, Boris and Natasha (Bullwinkle fame), and currently have Muddy (Waters) and Koko (Taylor), and have fostered Billie Holiday. The later were orphaned and have the blues. A friend of mine has a black cat named Voodoo (aka Voodles). Growing up we had the obvious "Blackie" cat.
If out of ideas, I go for famous musicians or cartoon characters.