The devlogs will answer some of your questions especially this one
https://wizardsofthecode.itch.io/soulash/devlog/81521/soulash-design-choices-and-its-future
You also might find some of the Suggestions and Idea's discussions interesting :D
The visual style is probably generally gonna be where it's at currently but I suspect the dev will probably play with the same kind of effects you see on the trees and bushes IE the stacked ASCII characters and 3D parallax effects in addition to the particle animations that are already there. Who knows, the modding update around 0.4 might also let us mess with textures and import custom sprites. Pretty sure you can already tinker around with the files and change icons, add map zones, abilities and creatures to your liking, but currently you'd have to keep backups of the changed files and incorporate them in again when patches come out. Lots of that I think will be loads easier later down the line :)