Well, you folks asked for it, so (for better or worse) here it is: The ZBrush 1.23 Green Thumb Tutorial.
It is in the form of an interactive ZScript that will draw this picture:
It's not much for art, but I've deliberately tried to use a variety of the techniques that I have employed in my images to date.
Just unzip the file's contents into your ZScripts folder. It includes a bitmap texture, which you want to leave in the same folder as the tutorial script in order for the program to run right.
Have fun, happy ZBrushing, and let me know if you find it useful!