Wait... this is all Witch Hat Atelier. Yes. You'd be right. I'm a fan.
This video has made me notice that a lot illustrations derive from the ability to draw hands and the face well. I spent the majority of my time drawing exactly that.
The illustrator and author of Witch Hat Atelier, "Kamome Shirahama" has uncompromised quality of work.
She consistently draws every part of her illustrations with attentiveness, inspiring me to become more observant to design of clothes, botanical, culture and story building.
It is more impressive that she also uses line art / inking, without any of her illustrations looking static from it.
All and all I know I can rely on Kamome for rich archive of references of all sorts.