This guide describes how to create an icon in Microsoft Paint. All you need to do is set a canvas, draw your icon, and save the file in .ico format.

You can now customize the icon shapes on your Pixel's home screen in the latest Android Canary release. Here are the options you're given.

In particular, the “Style” section would call existing themed icons “Minimal,” and add new “AI icon” and “Create” options. The strings regarding this say: ...