When designing a new plane, does aviation industry use style designers like car industry, or are the decisions made by aerodynamicist; will they solely determine what the plane will look like?
Notwithstanding the case that Quiet Flyer mentioned, generally no, because aerodynamic forms are inherently beautiful, so the need for dedicated stylists isn't there because an un-artistic designer striving for the best configuration will tend to produce an attractive shape by default (with exceptions of course, but overall). This tends to fit in with the old observation that beautiful aircraft tend to fly better than ugly ones.
Sometimes however, a particular contour, especially vertical fin shapes, become associated with a "brand" (since almost all airplanes are identified by their side profile) so the designer will conform to the brand shape to some degree. That doesn't take a dedicated stylist however.
The biggest example of automotive style styling practices infecting aviation I can think of is Cessna's entirely marketing driven change to their single engine line in the mid 60s, going from straight to swept vertical tails. Swept tails on 120 mph airplanes made a negligible difference to performance or handling (yes there is probably a theoretical benefit, but I've never seen any evidence that they made any practical difference that could be measured or observed and there is a significant manufacturing cost) but were done to look modern, since faster airplanes all had swept tails and they certainly do look sleeker. You will notice that they didn't also sweep the horizontal tail, just the vertical one, because no one cares about the view from below (lots of airplanes have swept horizontal tails; I'm just pointing out that Cessna saw no benefit to changing their single engine line this way).
Another one was "Omni-Vision" where turtle decks were cut down to add a rear window, partly for a more airy cockpit and visibility, and partly to look a bit more like a car. There was a significant drag penalty to Omni-Vision, costing a couple mph in speed when adopted vs the old straight turtledeck, but it was obviously considered worthwhile for both practical and aesthetic reasons as it became ingrained in Cessna's "brand".
In the 50s and 60s Cessna also adopted other (goofy) automotive marketing terms to describe useful engineering changes like adoption of steel gear legs, "Land-O-Matic Gear" (after acquiring Steve Wittman's leaf spring gear leg patent) so I think they probably brought in marketing types from the automotive industry, but I don't think dedicated stylists were necessary.
It depends on the aircraft. While not the norm, at least a few airplanes have been designed with input from "style" designers. At 4:58 on this FlightChannel video on You Tube about the Icon A5 amphibious lightsport airpane, we read that "the cockpit interior was designed by BMW designers, and the exterior was designed by Nissan designer Randy Rodriguez."