There could be. Many fanfic communities have works centered around diverse sexual orientations for various characters. For Loras Tyrell, given his character in the source material, it's likely that some fans have created gay - themed fanfics. You might try searching in relevant fandom forums or groups to get more targeted results.
There's a fanfic called 'Loras's Secret Love'. In this story, it focuses on Loras Tyrell's hidden gay relationship. It shows how he has to keep it under wraps in the society he lives in which is full of political intrigue and strict social norms. It's quite an engaging read if you're interested in this aspect of his character.
Common themes could include his place in society as a gay man. This might involve how he navigates the politics and social norms of his world while being true to himself. His relationships may also be a central theme, showing how they develop and grow over time. Additionally, themes of acceptance, both from himself and others, could be prevalent in these fanfics.
Loras Tyrell is an interesting character for gay fanfics because of his charm and status. He is a knight, known for his good looks and his skills. In the original story, his relationships are somewhat mysterious, which gives fanfic writers a lot of room to explore his potential gay relationships and the secrecy that might surround them.
Fanfiction.net is another place to look. There are many Game of Thrones fanfictions there. However, the search might require a bit more effort as the site is quite large. But if you search specifically for Sansa and Loras marriage fanfiction, you should be able to find some.
I also like 'Sansa and Loras: A New Alliance'. In this fanfiction, their marriage is not just a union of two individuals but also a strategic move for their families. It goes into great detail about how they navigate the power struggles within the Seven Kingdoms while trying to develop their own relationship.
In 'dark Sansa Stark fanfiction', Sansa can be more assertive. Unlike in the original where she is often a victim of circumstance, here she takes charge. For instance, she might not wait for others to rescue her but actively plot her own escape and revenge.
Sansa would be more assertive in her political moves. She has seen the consequences of inaction and bad decisions in the future. So, she would be quicker to make decisions that benefit her family and herself. For example, she might be more involved in military strategies to protect the North.
Another interesting one is 'A Pregnant Sansa in King's Landing'. This fanfiction takes a different approach. It focuses on Sansa's pregnancy while she's still in the heart of the political chaos in King's Landing. It shows how she uses her wits and strength, even in her pregnant state, to navigate the dangerous court politics.