The last scenes 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.
