A common theme is the clash of ideologies. The Coruscant Guard is often more tied to the political side, while the Jedi Commander follows the Jedi Code. For example, in many fanfics, they argue about how to handle a situation, like dealing with a separatist threat in the heart of Coruscant.
I've read a fanfic where a young Jedi Commander has to lead a group of Coruscant Guards into battle. It's an interesting take as it shows the inexperience of the Commander but also the discipline of the Guards. The title is a bit hard to remember, but it's a great read if you can find it.
They could be recording a Jedi training session. Young Padawans learning the ways of the Force under the guidance of their Masters would make for an exciting scene to capture.
In this fanfiction, perhaps Anakin defends the Jedi Temple from a sudden Sith attack. He might use his lightsaber skills and his connection to the Force to fend off the invaders.
In a Star Wars Jedi Temple Attack fanfiction, perhaps there's a traitor within the Jedi. This person helps the attackers, believing the Jedi have become too corrupt. The attack could lead to a great battle where Jedi have to fight not only the external foes but also deal with the betrayal from within.
One common theme is mystery. Since the Temple Guards are such enigmatic figures in the Star Wars universe, many fanfictions explore their hidden identities and motives. For example, some might suggest that they have a deeper connection to the Force than is initially known.
It could be a group of fallen Jedi. They turned to the dark side for various reasons, like power, revenge or disillusionment. As they were once Jedi, they know the temple's layout and weaknesses well, making them very dangerous villains in the attack.
One great 'Star Wars Temple Guard' fanfiction is 'The Guardian's Path' which delves deep into the backstory of a Temple Guard. It shows their training, their code, and how they interact with the Jedi Order in a really interesting way.
It could serve as a way to document a prophecy. If a Jedi has a vision of a future event, the camera crew's recording might be the only proof or way to share this prophecy with others in the galaxy.