Sure is. DDLC falls under the category of visual novels. It presents a story visually and allows the player to progress and influence the outcome through their decisions.
Well, start by getting really familiar with the characters and their personalities. That's key. Then think of an interesting plot or story arc that fits within the DDLC world.
One popular theme is the exploration of the characters' backstories beyond what's shown in the original game. For example, delving deeper into Sayori's depression and how it might have developed over time. Another theme is alternative universes, like a world where Monika isn't self - aware and the club functions 'normally'. Friendship among the club members is also a common theme, showing how they support each other through various situations.
One interesting DDLC fanfic could be 'A New Perspective in DDLC'. It might explore the characters from a different angle, like how the side characters interact when the main plot isn't focused on them.
Archive of Our Own (AO3) is a great place to start. It has a large collection of DDLC fanfics with different themes and ratings. You can search by tags like the character's name or the specific theme you're interested in. Another option is FanFiction.net, which also has a decent number of DDLC fan works. Just be aware that the quality may vary more widely there compared to AO3.
One interesting concept could be creating unique OCs (Original Characters) with their own backstories that interact with the existing DDLC (Doki Doki Literature Club) characters in unexpected ways. For example, an OC who is a transfer student and has a mysterious past that somehow links to the club's secrets.