I decided a long time ago that I wanted to create my own screentones, no real underlying reason, that's just how I am. I had about eight for a while but slowly I'm building my library. This is the first set of 30, they're all pretty basic, I haven't started on any really unique ones yet (altho two here were total accidents and turned out to be pretty original I think). Since I created them and can make them as big, small, dark or light as I want or alter them on the fly, it turns out they can be pretty versatile in illustrations that means it may turn out to be a little while before set number 2 comes into being.
Nice set. Being able to size them on the fly does sound quite useful. I'm always annoyed when I have to stop in the middle of painting to rework a brush pattern.