For some reason it's really hard for me to imagine a simple and clean world like the thumbnails below. I'm just used to playing around with brushes... But I think 1 and 3 (left side) are pretty close to what I'm aiming for. I definitely need to decide my colour palette, because this proved to be problematic as well. The way I used colours don't quite work well so I will have to select them carefully in order to bring the harmony I want to have.