I used to do this, too many decades ago now (won't reveal my age lol). Nothing as gorgeous as what you're achieving, but I'd just sit and create a "collage of pen doodles" until something emerged. It was always very organic and not thought out at all. Did something similar but different by using a black pen and ruler and making lots of lines to create scenes too...whole cityscapes would emerge. Everyone else my age were out partying! or socializing.
