Hi Tyourai,
Minifantasy is a community-driven collection, so new Minifantasy asset packs are suggested and voted on by the Minifantasy Patreon community. Every month I work on the asset pack that the majority of the Patrons chose.
The community already suggested a pack with more spell effects, but it didn't get enough votes yet in the monthly polls. However, there is interest (it has gotten quite a lot of votes in the last couple of months) and it's just a matter of time before that asset pack gets in the making :)