The plot of Revenge of the Sith centers around the final stages of the Clone Wars and Anakin Skywalker's descent to the dark side. It's a complex and intense story with lots of action and drama.
One of the main themes is the fall of Anakin Skywalker. His journey from a Jedi Knight to Darth Vader is central. Another theme is the collapse of the Republic. The political intrigue and manipulation that lead to its downfall are explored. Also, the theme of friendship and betrayal is there, as Anakin betrays his friends and the Jedi Order.
Definitely Anakin Skywalker. He's the one who goes through the most drastic change. Then there's Palpatine, the mastermind behind the Sith's plan. Obi - Wan Kenobi, who has to face his former apprentice. And Yoda, the wise Jedi Master who tries to counter the Sith's plot. Also, Padmé, whose love for Anakin is a key factor in the whole drama.
One idea could be exploring what would have happened if Anakin had a different mentor during his fall to the dark side. Maybe a Jedi who was more in tune with his emotions could have guided him better.
Shaak Ti. She was a powerful Jedi, but not much was explored about her in the movie. In fanfiction, you could delve into her backstory, her relationships with other Jedi, and how she might have reacted to the events of the Clone Wars and Anakin's fall. For example, she could have had a secret mission to uncover the Sith's plot that was cut short by Order 66.
One popular type of Star Wars Sith Temple fanfiction might involve a young Jedi who is lured to the dark side after exploring the Sith Temple. They could encounter ancient Sith artifacts that whisper to them, gradually corrupting their once - pure intentions.
I'd recommend 'Sith Apprentice: Legacy of the Dark Side'. It's a story that focuses on an apprentice who discovers an ancient Sith artifact and the chaos that ensues. It's full of mystery and action.
One possible fanfiction could be about a Sith Lord from Star Wars ending up in the Naruto universe. Maybe he tries to use the Force to control the chakra, but finds that it's a completely different power system. He could then form an alliance with some of the villains in Naruto, like Orochimaru, who are also interested in power and dark arts.