A New Hope

A number of design elements in A New Hope illustrate the contrast between the Empire and the Rebel Alliance.

The Imperial forces exhibit an extreme degree of standardization.  Barring different heights, each stormtrooper or TIE pilot looks exactly like any other.  While the Rebel forces wear uniforms too, they're not so restrictive that the individual's identity is obscured.  (This difference between the two factions is shown most clearly in the battles that bookend the movie, the boarding of the Tantive IV and the Battle of Yavin.)

The construction of the Death Star is completed during the course of the movie, so it couldn't be any newer.  The equipment that the Rebels use, however, shows its age, especially the Y-wings.

The groups' respective headquarters also differ in that the Death Star is artificial and somewhat isolated in space while the Rebel base on Yavin IV is constructed primarily of stone (a natural material) and located in the midst of a jungle.

Even in their appearances, then, the Empire and the Rebel Alliance oppose each other.

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In the scene where Obi-Wan gives Anakin's lightsaber to Luke, he also briefly comments on the Jedi:  "For over a thousand generations, the Jedi Knights were the guardians of peace and justice in the old Republic, before the dark times, before the Empire."  Luke de-activates the lightsaber at the end of Obi-Wan's remark, and in a small way, this extinguishing mirrors the Jedi's near extinction.

Revenge of the Sith

The last scenes of Revenge of the Sith show the four members of the Skywalker family.

Padmé at her funeral procession:

Anakin, now Darth Vader, watching the construction of the Death Star:

Leia on Alderaan:

Luke on Tatooine:

Various aspects of these scenes highlight how Vader now differs from the others.

Padmé, Leia, and Luke are each accompanied by family, but Vader joins the Emperor and Tarkin, powerful figures in the new Empire.  Since Padmé's dead and Leia and Luke are infants, they're mostly passive in these scenes (Luke seems to be asleep), but Vader strides down the bridge of the Star Destroyer.  In contrast to the natural locations the others are shown in, Vader's environment is completely artificial (as if to match Obi-Wan's "more machine now than man" comment in Return of the Jedi), and while the colors on Naboo, Alderaan, and Tatooine may not be particularly vivid, there's a greater variety in each than on the Star Destroyer bridge, which is primarily grayscale.

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During Anakin and Obi-Wan's duel over the lava on Mustafar, Anakin uses the Force to control a mining droid* so that, standing on top of it, he can move closer to the platform where Obi-Wan is and continue the fight.  In a small way, this imposition of his will upon the droid demonstrates a quality that's part of his character now that he's turned to the dark side (his "lust for power" as Obi-Wan calls it).  As Anakin told Padmé shortly before this, they can now "make things the way we want them to be."

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*I have to credit LEGO Star Wars in 100 Scenes (p. 94) for pointing this out to me.  In the movie, what Anakin is doing isn't as obvious, but when he leaps from the droid's head to the other side of Obi-Wan's platform, the droid zooms off on its own again, suddenly released from Anakin's hold.

The Phantom Menace

There's some small significance in Qui-Gon's syntax in the scene in The Phantom Menace where he asks Obi-Wan to analyze Anakin's blood for midi-chlorians.  Obi-Wan is surprised by the results:  "The reading is off the chart, over 20,000.  Even Master Yoda doesn't have a midi-chlorian count that high."  Qui-Gon replies, "No Jedi has."  His response exhibits ellipsis; for brevity, he leaves out some words.  In full, it would be "No Jedi has a midi-chlorian count that high."  In a way, however, this elision matches the context.  The omission in Qui-Gon's remark is similar to how other Jedi's midi-chlorian counts fall short of Anakin's.  There's a lack common to both.