This thread seems to be about 2 related, but different subjects. Does sexuality book bands (Britney, Spice Girls) and does appearence, in general book bands, (Merv Griffin, Miles Davis).
IMHO I'd have to say that sexuality does play more of role than simple appearence. Whether it actually gets you in the door or keeps you out is another issue. I know of people who are contemptuous of Kathryn Tyckell's publicity photo -- the one of her in the leather jacket with the rather sultry/bewildered look on her face: I know others who more-or-less salivate.
As for appearence in general, I remember a friend of mine commenting how Garth Brooks didn't look like a CW singer; short, and kinda chunky. I'm looking at a picture of Kate Rusby on Hourglass and she's not what I'd call "stunning"; attractive, certainly. Of course, what ultimately grabbed my attention was the stunning musical and performance talent all of the above -- Tyckell, Brooks and Rusby -- display. Is it perhaps more accurate that appearence, and for that matter sexuality, counts more towards starting out than it does in continuing a career?