Incorrect. I've been using the B'Rotlh skin on my T5 all this time. But can confirm that the new T6 does not show the B'Rotlh skin as an available option.
I only have one character, my KDF K'tala, daughter of Hogoth, of House Grilka, but I would want to use Charlize Theron. I think she could pull off a good Klingon. :)