What role, if any, does visual aesthetics play in the design of modern airliners? Another way of asking the question: 


  Are there any distinctly identifiable features of particular modern airliners that are there for design reasons that have less to do with engineering than with appearance?


or:


  Could one look at at a modern airliner, and point out something in its design, however small or large, that is there because "it looked good"?


To be clear about a few points:


By modern I mean since the 707.
In visual aesthetics I only want to include physical form - contours, placement of parts, proportions etc - and specifically want to exclude livery, colour, and so on.
I'm not interested in inessential matters like the design of the interior, but in the airframe, engines and so on.


I'd be pretty surprised to discover that any aspects of design allowed aesthetics to trump engineering consideration, but perhaps there are examples where aesthetics played a part because the choices, from an engineering point of view, were equally viable.
A friend of mine, who did the design of the Gulfstream G650 canopy, designed the cockpit windows on that jet after the lines of an Aston Martin sports car.  I suspect there are a few other features like that in various aircraft.

That being said, despite the aircraft design mantra of 'if it looks good it will fly good' most the the design choices made in aircraft is very utilitarian.  Aerospace engineers - and in particular the management at the major OEMs - are some of the most boring, unimaginative SOBs you will ever meet.  They generally leave creativity to the marketing departments and make every effort to pound flat any nail that sticks out.

The only exception to that rule that I can think of was Burt Rutan of Scaled Composites, who when his own way and designed unique planes as virtual works of art - but also were highly functional with great performance and capabilities.  From the Vari-EZ to Spaceship One, that guy is in a league of his own.