One common theme is identity. Lincoln has to figure out who he is now as a vampire while still being part of the Loud family. Another is secrecy. He has to keep his vampire nature a secret from his family and friends at first. And there's often the theme of power. His new vampire powers and how he uses or struggles with them.
Yes, there are some interesting ones. You can start by looking on fanfiction platforms like FanFiction.net or Archive of Our Own. Just search for 'Loud House Lincoln Vampire' and you'll likely find a variety of stories with different takes on Lincoln as a vampire in the Loud House universe. Some might focus on his relationships with his family members in this new, vampiric state, while others could be more action - oriented with him facing off against other supernatural beings.
One great Loud House Lincoln fanfiction is 'Lincoln's New Adventure'. It takes Lincoln on a journey outside of Royal Woods where he meets new friends and has to face some unique challenges. It's really exciting as it shows a different side of Lincoln's character.
There might also be some original characters created specifically for the fanfiction. These could be other humans who know about Lincoln's secret or other supernatural beings that are related to the vampire lore in the story.
There could be many interesting fanfictions about Jordan and Lincoln in the context of Loud House for girls. Maybe it could be a story where Jordan and Lincoln team up to solve a mystery in the Loud House. For example, they might be trying to figure out why strange things are happening around the house, like objects moving on their own or mysterious noises at night.
One idea could be a story where Lincoln and Lola have to team up for a school project. At first, they bicker as usual because of their differences. But as they work together, they start to understand each other better. For example, Lincoln realizes that Lola is not just a pageant - obsessed girl, and Lola sees that Lincoln has his own insecurities and strengths.
There's also a fanfic where Lincoln discovers he has vampire heritage. In this story, he struggles to keep it a secret from his large family while also exploring his new powers. It's an interesting take on the character as he tries to balance his normal life with this new, supernatural side.
One possible fanfiction could be where Lori, as a vampire, struggles to keep her identity a secret within the Loud House. She might have to deal with her newfound cravings for blood while trying not to alarm her family. Maybe she forms an unexpected alliance with one of her siblings who discovers her secret and helps her find alternative ways to satisfy her thirst without harming anyone.
One common theme is family dynamics. Lincoln often snaps due to the chaos in his large family, like dealing with his sisters' different personalities and the constant noise at home.
One possible fanfiction could be that Lincoln constantly has bad luck in his attempts to get some alone time in the house. For example, every time he plans to have a quiet reading session in his favorite corner, one of his sisters accidentally spills something on him or makes a lot of noise right there. It could also be that his bad luck extends to school, where he always seems to be the one picked on by the teacher for things that are not his fault, like when his classmates play pranks and he gets blamed in the Loud House Lincoln - bad luck scenario.