You can start by searching on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just type in 'Twilight Jacob Black fanfiction' in the search bar and you'll get a bunch of results. You can also join Twilight - related fan groups on social media platforms. Members often share their favorite fanfictions there.
To incorporate their different worlds, you could start by having Jacob Black enter Billie Eilish's concert in a dream. In the dream, her music has a magical quality that draws him in. Then, when he wakes up, he starts to notice strange things in Forks that seem to be related to the dream. For example, he might hear her music faintly in the forest when he's in his werewolf form.
One great 'Twilight Jacob Black fanfiction' is 'The Other Side of Jacob'. It delves into Jacob's inner thoughts and his struggle with his wolf nature in a really interesting way. Another is 'Jacob's New Path' which shows a different journey for Jacob after the events in the original series. There's also 'Moonlit Encounters with Jacob' that focuses on his relationships in a new and exciting light.
Love is a very common theme. It shows the deep, often instant connection between Jacob and his mate. Another theme is loyalty, as they have to be loyal to each other in the face of various challenges.
In some fanfictions, Jacob's imprint can be a catalyst for a larger story. Maybe the imprinted one has a special power or a secret past. This can draw in other characters from the Twilight universe and create a more complex and engaging plot as everyone is involved in uncovering the mystery around the imprinted person.
One interesting fanfiction could be about Jacob's journey after imprinting, how he copes with his newfound bond. For example, a story might explore his relationship with the imprinted person in the face of the complex vampire - werewolf dynamics in the Twilight world.
Because the author's plot focused on other relationships. Jacob was meant to be connected to Renesmee, and Leah had her own role in the werewolf pack's story.
Perhaps in this fanfic, Jacob Black is a big fan of Billie Eilish in his own world. One day, he discovers that her music has the power to break the curse that ties him to his werewolf form. He then embarks on a journey to find Billie Eilish in the human world to ask for her help, facing many challenges along the way, like hiding from vampires who don't want him to be free of the curse.
In some Twilight fanfictions, Jacob's werewolf form might be described as larger in terms of physical stature compared to Emmett's vampire form. Maybe it's about his height, or his overall build when transformed. For example, his werewolf shape could be more bulky and take up more space, while Emmett, though strong as a vampire, might be more streamlined in comparison.
Another way is through physical manifestations. In some fanfiction, Jacob's pain might be shown as a physical ache in his wolf form, like a constant throbbing that won't go away. Leah's pain could be shown as a sort of weariness in her eyes or a slump in her posture, indicating the emotional burden she carries day in and day out.