There is a lot of prepared and approved SVG icons for OSM-Carto just wainting to be added, but there is unfortunately also lack of people ready to add these new features. We would like to invite you to improving default OSM style.
Here is a task list: https://github.com/gravitystorm/openstreetmap-carto/issues/3298
Coding instruction links:
You can also ask for any help in certain tickets and PRs :)