You can try looking on fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. These platforms have a vast collection of fan - made stories, and you might be able to find some great Lucy and Laxus married fanfiction there.
Some fanfictions might focus on how they first fell in love before getting married. It could involve a series of adventures where they gradually realize their feelings for each other. Maybe a dangerous mission where they have to rely on each other a lot, which sparks the initial attraction.
I'm not sure of a specific one off the top of my head, but you could also try looking on Archive of Our Own (AO3). It has a large collection of fanfictions. Some stories might have them getting secretly married due to various reasons like to protect their guild or because of a secret mission they are on together. This adds an interesting layer of mystery and drama to their relationship.
Natsu would probably be really excited and might even challenge Laxus to a friendly fight right at the wedding reception, just for fun. Happy would be flying around, dropping flower petals everywhere and congratulating them. Erza would be very happy but also very strict about the wedding protocol, making sure everything is perfect. Gray would be a bit more laid - back, but still offer his congratulations with a cool smile.
One possible plot twist could be that an old enemy resurfaces on their wedding day, threatening to disrupt the ceremony. Maybe a dark guild that Laxus once fought against comes back for revenge. Another twist could be that Lucy discovers a hidden family secret that might change her relationship with Laxus. For example, her family has some sort of connection to Laxus' past that she was unaware of. And a third plot twist could be that a magic spell goes wrong during the wedding, causing everyone to swap personalities for a while, which would lead to some really interesting and comical situations.
One common theme is secrecy and the challenges it brings. They have to keep their marriage from others, which can lead to some really tense situations.
Some people also recommend following specific Fairy Tail fanfic writers on social media platforms. They might announce when they've written a new Lucy x Laxus piece or share links to their works. Additionally, if you're part of a Fairy Tail fan club or group, asking around there could lead you to some great fanfictions.
One common theme is friendship. They often start as acquaintances or even rivals and gradually become friends. Another theme is adventure. They go on various quests and battles together in many fanfictions.
One great Laxus and Lucy fanfiction is 'A Bond Beyond Guilds'. It focuses on how they team up for a difficult mission and gradually discover a deep connection. Another is 'Laxus and Lucy: The Unexpected Alliance' which shows how their different powers complement each other in unexpected ways. And 'Lucy's Encounter with Laxus' is also interesting as it delves into their first meeting from Lucy's perspective.
There could also be other supporting characters from the Fairy Tail guild. For instance, Mirajane might play a role in giving advice to Lucy about pregnancy and motherhood, since she has a nurturing side. And Makarov, as the guild master, could be involved in ensuring the safety of Lucy and the future of the guild with a new member on the way.