Another author could be RoseRed. She often writes fanfictions that are full of action and adventure. In her Damon and Katherine baby fanfictions, she might create exciting plotlines where the baby is in the middle of some dangerous vampire battles. Her stories are fast - paced and keep you on the edge of your seat.
There might be a fanfiction where Damon and Katherine's baby is raised in a different era. For example, the baby is sent forward in time and grows up in a modern world. This would lead to a lot of culture shock and interesting interactions as the baby, now grown, tries to understand its vampire heritage while adapting to the new world. It could also bring about a reunion with Damon and Katherine in a very unexpected way.
Caroline would likely be a mix of excited and cautious. She's a bit of a romantic at heart, so she might see the potential for a new family dynamic. However, she also knows Katherine's past and would be on guard to make sure Katherine doesn't manipulate Damon during the pregnancy. She would probably try to befriend Katherine to keep an eye on things.
There are fanfictions where Katherine returns from the dead in a different form, perhaps as a spirit. Damon, who has always had a deep connection with her, has to figure out how to interact with this new version of Katherine. It could involve a journey of self - discovery for Damon as he realizes that his feelings for her are more complex than he thought, even in this new and strange situation.
Katherine herself is also a great character in fanfiction. Her devious and manipulative ways add a lot of drama. In some fanfictions, her backstory is delved into more deeply, showing how she became the way she is. This can make her a more sympathetic or even more despicable character, depending on the writer's take.
One great Damon and Katherine love fanfiction is 'Eternal Bond' which delves deep into their complex relationship. It shows how their love is intertwined with power struggles and dark secrets.
Perhaps the pregnancy is a sign of a new vampire - related phenomenon. In the fanfiction world, it could be that a new type of vampire is emerging, and Damon and Katherine are the first to experience this pregnancy. This could lead to them being hunted by other vampires who either fear this new development or want to study it for their own gain.
In the fanfiction, perhaps the baby's birth is a very difficult and dangerous process. Since both Bella and Damon are from different fictional universes with their own set of rules regarding vampires and such. The baby could be a symbol of a new beginning for their relationship, forcing them to put aside their differences and work together to protect their child. They may have to face challenges from both the vampire and human communities who are either afraid of or envious of the baby.
The Originals' enemies, like the werewolves, could be antagonists. They might see the baby as a symbol of the vampires' growth and power and try to harm it. Also, some of the other vampire factions who are against the Mikaelsons could target the baby to get back at Elijah and Katherine.
Archive of Our Own (AO3) is also a great place to look for such fanfictions. There are numerous well - written stories there that explore the Damon - Katherine relationship from different angles. It has a good search function which allows you to filter the stories based on various criteria like rating, word count etc.