One might not realize the unique aesthetic of Star Wars at first glance. It is a movie done largely in the traditional Hollywood "invisible" editing style. This is meant to make a seamless viewing process for the audience. Nevertheless, with enough digging, one can find an aesthetic in anything. I will only bring up two signatures of Star Wars. The first is the opening title crawl. It is something that no one at the time and I can't recall anyone since using. The second is the scene transitions. Many involve showing a setting before moving in, often with some form of action, such as a flying spaceship, involved. I guess this could be considered a form of establishing shot. Also, as a throwback, George Lucas brought back the wipe for a scene transition. The wipe was so old it was new.
Perhaps the most important element of the entire Star Wars saga, including Episode IV, is the music. It is arguably the most iconic film score of all time. Right from the beginning, you are taken to a new universe through the power of music. The entire movie is a reel-to-reel music soundtrack. Some of the most prominent themes include, Leia's theme, the Skywalker theme and the opening title, not to mention the jazzy works of the cantina band. Each theme conveys a certain mood, but is never generic. The music touches on universal feelings and is used to heighten scenes, but is also distinctly Star Wars. The themes are not only distinctly Star Wars, but distinctly the characters to which they are tied. They move in and out in variations according to which characters the scene belongs to.
One of the greatest scenes in the entire Star Wars saga is the cantina scene. It does so much to create a sense of universe, an entire article could be written on that scene alone. It certainly already has the element of unique music, but it also has the element of setting. The first thing that happens in the cantina is that we the audience are shown all the different alien peoples in the cantina. At no point will these people be truly relevant to the story or will we get to know them, but they all add atmosphere. There are probably about fifty different interesting stories taking place in that cantina at that very moment that we the audience would love to see, but we can only imagine. Elsewhere in the film, we see the Lars moisture farm, Mos Eisley, the Death Star and the Massasi ruins of Yavin IV. Each scene is thoroughly detailed with extras going about their business. One of the greatest touches in creating a unique environment is the two suns of the desert planet Tatooine. They are part of the reason that scene is so powerful. Many of the scenes from A New Hope were shot in the Tunisian desert and Guatemala, using location shooting to create a new world.
Throwaway conversations have some part in Star Wars, although the story has to move. There is a mix of throwaway conversations and the entire movie being peppered with throwaway references to things unseen. On the Death Star, there is talk of the Imperial Senate being dissolved. Obi-Wan talks to Luke about the old days of the Jedi Knights and the Force, creating a mystery that would end in disaster. An important element of the throwaway elements in this completely fantasy universe is the acting. Han Solo says "You've never heard of the Millennium Falcon? It's the ship that made the Kessel run in less than twelve parsecs." I count two, possibly three pieces of made-up crap, but Harrison Ford sells it naturally. The whole movie is loaded with small throwaway references like this that create a universe without destroying the pace.
The last means of creating a universe is used by the Star Wars saga in general. This is the creation of a franchise. The very first movie, Episode IV, does the most of creating a feeling of universe because it has to. It introduces the universe. It has a spontaneity the other movies don't because the main players are not established yet. The later movies of the original trilogy work more on character development. They also give us new settings and adventures, while holding on to an appropriate level of familiarity and continuity with the original.
The examples of universe creation in Star Wars: Episode IV- A New Hope are virtually omnipresent throughout the film. It is the sign of a great creative mind that he created a universe and back story, but did not play all his cards within the finished film. It creates a larger world where the audiences imagination soars.