E! Online has a quote from costume designer Deirdra Govan :
Mr. Blank's finalized look, which includes a bowler hat and eye patch,
was a combination of how Boots and Deirdra saw the character. Boots
wanted to use a leather shop in Oakland for the patch and Deirdra
pushed for the hat.
"Mr. Blank was a really interesting character, in that he has no
backstory," the costume director shared. "He's just a man that
appears. For me, having studying art history and understanding
surrealism, the film itself is very surreal. I took that straight to
the place in Renee Magritte. You have a man that has no clear name.
Even though we see his face, he's still a man without an identity."