A really interesting fanfic concept could be where the dragons from Dragon Maid are mistaken for powerful summons in the Naruto world. And the Naruto characters have to figure out how to deal with these strange, sentient summons. It could lead to a lot of humorous and action - packed situations as the two groups try to understand each other.
One popular idea is exploring different dragon cultures in the fanfic. Since the series has various dragons with their own unique traits, fanfics might delve deeper into how these dragon cultures function, like their social hierarchies or mating rituals. Another idea could be focusing on the daily life of Kobayashi and Tohru in more detail, such as how they handle holidays or special occasions that are important to dragons but new to Kobayashi. Also, some fanfics may create new dragon characters and explore their relationships with the existing cast.
A common theme is family. Kanna is often depicted as becoming part of Kobayashi's family, and fanfics explore how they interact as a family unit. Another theme is friendship. Kanna makes friends in the human world, and these relationships are often a big part of the stories.
Character development is key. If the fanfic shows how the Naruto characters grow and adapt in the world of Dragon Maid, or vice versa, it's more engaging. For instance, if Naruto has to deal with the laid - back attitude of some of the Dragon Maid characters while still maintaining his own values. Also, an interesting plot that takes advantage of the differences between the two universes, like a threat that only the combined powers of both worlds can defeat.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of 'Kobayashi - Dragon Maid' fanfics, and you can search by tags such as the character names, the type of relationship you're interested in (like friendship or romance), or the genre of the fanfic (such as comedy or drama).
Family is a big theme too. The maids and Kobayashi form a sort of family unit. In some fanfictions, they celebrate human holidays together like Christmas or New Year's, showing how they've become a family. Also, the theme of self - discovery is present. Dragons learn more about their own identities and powers as they interact with the human world. For instance, Kanna discovers new things about her dragon heritage while at school.
One great 'Ms Kobayashi Dragon Maid' fanfiction is 'A New Beginning'. It adds a really interesting new adventure for Tohru and Kobayashi, exploring Tohru's past in more depth.
Another option is to check out some official fanfic anthologies if there are any. These are more likely to be free of any inappropriate content. They might contain stories that expand on the backstories of the characters, or new little adventures that the characters go on together in the 'Kobayashi - Dragon Maid' universe.