My advice (also not on the interview panel ) is to be as conservative as you feel comfortable. Don't go for the stubble look at the interview and do be dressed smartly. I realise suits and ties are not in these days, but looking 'professional' will set the right impression and how you are dressed is looked at by the interview panel - after all this is they way the panel will assess how you present yourself to our owners when you fly them (shoes clean, neatly groomed, hair brushed, nails clean, tie straight if you wear one, etc). You will be the face of the company and not behind a locked cockpit door for the flight.
Facial hair is a personal choice, but as stated earlier, beards and 'tasches must be grown during off time - no 'Lemmy's' (look up Motorhead if too young) or Zapatas (mexican bandit) but goatee is OK.
Good luck to all and if you make it through to Indoc, please dress smartly there as well - don't turn up looking like a bag of s**t - unless you luggage is lost by the airline of course!