I have a long term, 'custom' hobby project in the works in an effort to add another dimension to my Chaos Knight army, and to attempt to consolidate some of my other Chaos miniatures in an interesting way.
I think one of the most fascinating regions in
40K (and relatively unexplored in lore) is the Maelstrom. Not quite part of the warp, not quite part of real-space, it sits in both simultaneously. Looking into the region, I came across an article on a character called Kaarja Salombar, she's a little known 'bit part' character from one or more
40K novels, and no longer living, but remains exceedingly interesting.
Kaarja was known as the 'Corsair queen', and commanded a large pirate (I'm a sucker for pirates and the golden age of piracy has long been a passionate area of study for me,) fleet and warband. Notably, she had ties with the Red Corsairs and appears to have been a half human, half aeldari hybrid.
Knowing she's dead, I took to wondering what happened to her (relatively large) warband. Did she have a daughter, or sister who inherited her status and became the next 'Corsair queen'?
As a hobbyist, I'm far more a painter and modeller first, and player second. I love diversity in armies rather than endlessly painting the same schemes, so am looking at making my existing Knights a diverse, Dreadblade lance that have flocked to the warbands banner, rather than a holistic 'Household'.
My favourite aspect of painting, is freehand work on vehicles, and I love the tradition of 'nose art' on aircraft. This will likely be the element that ties the Knights (and other vehicles) together.
Finally, I find terrain to so often be an element of the hobby that's left to one side. I really want this force to inhabit a 'living world' on the board, and have terrain they can fight from and defend in a game. I'm hugely inspired by the art of Ian Mcque
https://www.this-is-cool.co.uk/wp-content/gallery/ian-mcque/ian-mcque-fantasy-scifi-artist-24.jpg and have this rough concept for a very 'old meets new' outpost, with worn canopies (sail-like) and a good amount of misuse and decay.
Early stages, with much of it still 'in concept', but I've been converting troops for the 'foot' warband, and several Knights are in various stages of completion.