One common theme is acceptance. The vampires are trying to be accepted by society or at least by a small group within it. Another theme is redemption. They are reformed, so they are often seeking to make up for their past actions as vampires.
Sure. One popular piece might be 'The New Life of a Reformed Vampire' which focuses on a vampire trying to adapt to a more 'human' lifestyle within the support group. It has interesting character development and shows the struggles they face.
One common theme is the struggle with identity. Harry, being a vampire, has to deal with a new side of himself that he may not fully understand at first. For example, in many fics, he has to figure out how to balance his wizard self with his vampire instincts.
One common theme is the struggle between humanity and vampirism. When Ash is involved, it often shows his fight to keep his humanity intact even in the face of vampiric allure.
The theme of the outcast is also prevalent. Despite her power and allure, the vampire seductress is often an outcast in both the human and vampire worlds. Humans fear her, and vampires might be jealous of her power or see her as a threat. This sense of not belonging adds depth to her character and is often explored in different ways in fanfictions. For instance, she might try to find a place where she can be herself, or she might use her outcast status to her advantage by creating her own rules and living on the fringes of society.
Another theme is love and relationships. Since he's a vampire, his relationships with other characters, whether it's romantic or platonic, are often complicated. There might be a love interest who has to come to terms with Todoroki being a vampire, like in 'Todoroki's Vampire Love Affair' where the female lead has to navigate her feelings while also dealing with the danger that comes with Todoroki's vampirism.
A sense of otherworldliness is another theme. Vampire hypnosis fanfiction often plays on the idea that the vampire's world is different from the human world, and the hypnosis is a bridge between the two. In stories like 'The Otherworldly Hypnosis of Vampires', the hypnosis not only affects the human's mind but also gives them glimpses into the vampire's strange and alluring world, full of different rules, powers, and social hierarchies.
The theme of redemption can also be present. Sasuke may have a dark past as a vampire, and through his relationship with Sakura, he may seek redemption. This could involve him trying to control his vampiric urges or make amends for past actions.
In RWBY vampire fanfiction, a frequently seen theme is the clash of cultures. The RWBY world has its own set of values, and vampires bring in their own set of rules and behaviors. This can lead to interesting interactions and conflicts. Another theme is the search for a cure. If a character is turned into a vampire, they or their friends may be on a quest to find a way to reverse the transformation. And the theme of outcasts also exists. Vampires are often seen as outcasts in the RWBY world, and this can be explored in terms of how they deal with being shunned by society and how they form their own communities or try to integrate into the existing ones.
A common theme is the clash of two different worlds. Sonic represents speed, freedom, and heroism, while vampires often symbolize mystery, darkness, and immortality. So, there's often a struggle when these two meet.
One common theme is the struggle between good and evil. Since Willow was originally a good witch, as a vampire, she often battles her new vampire nature which is associated with evil. Another theme is redemption. Many fanfictions explore whether Vampire Willow can be redeemed and return to her former self or at least find a new moral path. Power is also a theme, as being a vampire gives her new powers and she has to learn to control and use them.