Love and redemption are common themes. Their relationship in the original story had its share of problems, so in fanfiction, they often find ways to redeem themselves and fully embrace their love.
There's a fanfic titled 'Atlas and Lily: Forever After' which is really good. It focuses on their journey together, how they build a life in the small town they both love. It has some really sweet moments between them that are a delight to read.
One common theme is friendship. Their relationship is often explored in depth, showing how they rely on each other. For example, in many stories, they help each other out of difficult situations.
Adventure is also a big theme. They go on all sorts of quests, whether it's exploring a mysterious cave or traveling to a far - off land. In these adventures, they learn more about themselves and each other. Another theme is discovery. This could be the discovery of a new power, as in the case where Lily might find she has a special ability that Atlas helps her understand and control.
A popular one is 'The Journey of Lily and Atlas'. It's a heartwarming tale that starts with their chance encounter and then follows their growth as individuals and as a duo. The author does a great job of creating a believable world for them to inhabit.
One great Atlas and Lily fanfiction is 'Atlas and Lily's Adventure'. It takes them on a journey through a magical forest filled with strange creatures. Their relationship develops as they face challenges together, like when they have to solve a riddle to cross a bridge.
One idea could be exploring what would happen if Lily and Ryle had met in a different context, like in a different city. Another could be writing from Atlas's perspective during his time away from Lily, detailing his struggles and growth. Maybe also a fanfic where Lily's mother had a different influence on her relationship choices.