The people start off looking pretty good when hired, like a group of kids in college would look, but then it's mostly all downhill from there.  ....Believe me, after 4-5+ months of full-time work, the 1st years are busy doing physical inventories all over the region, and at the Christmas holiday party, everyone's got tired eyes with grey underneath, possibly extra 10-30+ pounds on them, bad breath, coffee breath.  Even at 1st year training kids are downing coffee like water to stay awake.

When I got a tour of the big4 office, I got an offer but a 1st year gave me the tour of the big4 office HQ and she was generally good looking but she looked tired and her breath was bad.

They also try to accept close to 50% women, especially in audit, and there are generally fewer women accounting majors to begin with at the colleges, so it's definitely easier to get in if you're a woman.  If you're an underrepresented minority that also helps.  As far as whether looks make a difference, they always do.  How much?  You'll never know.  You're an employee at will. 

If they decide they don't like your shirt, that could be the end right there. Id say looks and generally polished look stuff make more of a difference if you're applying to big4 because they want people who don't know anything yet but just have enormous drive and energy, excellent social skills, and willing to learn.  Plus they know after 1-2 years most people will be gone

It's client service business...what do you expect?

If you were HR talent at a big4, you would look for the same things.  You dont need to show you know much about accounting but more that you are good with people.

  The return on investment from HR's perspective is mostly the 1st 1-2 years because everyone at big4 is GONE for the most part after that....

To get big4 interview -> excellent GPA at a reputable program 3.3 gpa+ is perhaps minimum (there are exceptions though)...3.5+ (decent) where the big4 make a good selection for interviews.., sometimes a bunch are from Beta Alpha Psi honors fraternity. Low-level work experience such as working part-time in retail or at a restaurant where you dealt with customers looks great on your resume believe it or not because you can use it for stories in the interview. 

Once you get an interview it's -> your GPA is already good enough and got you in, but don't assume you got an offer just because you have a 3.9gpa.  otherwise you may get beat out by tons of 3.3 gpa types.  at the interview, to beat out others selected for interview, you need decent to above avg+ looks, good polished appearance and professionalism, enormous drive and energy, excellent social skills, willingness to learn, very easygoing - can get along with the most difficult of personalities, willingness to learn and someone who will suck up to authority...also, you have to come up with specific examples.  above all you need to come across as genuinely nice person who is great personality/great working in teams/dealing with ambiguity... 

1st year auditor at big4 - you mostly help out ticking and tying numbers, make copies/errands,  and ordering lunch for people.  This one time I had to order a cheeseburger for the partner but partner is too busy/stressed so you cannot ask the partner how he wants it cooked so you just get it well-done. Nice and black like a greasy flattened hockey puck.  Partner graduated from college in the 1980s but already looks like your grandfather.  He's obese and extremely stressed. That's what I did.  He don't like well done burgers? Too bad

Good luck!

Case in point - a family member of mine is an exec at a Fortune 500 and hired Deloitte Consulting....at a big meeting D.Consulting brought along a couple people - a senior person and an extremely good looking 1st year male consultant/"Analyst" who while extremely good looking (like a model) was otherwise useless, didnt know jack, etc.  I dont think he is dumb but Ithink he was just a 500/hr BS'er who really had no clue what he was talking about.  and he had to just make himself sound like he did...sometimes you have to talk to the client and just be full of hot air.  So this company thinks these consultants are an enormous waste of $ and wont be using them again.