I've been following the CSS in-depth course by Estelle Weylon Frontend Masters to learn much of this stuff. I recommend you go check out her work. The slides she use while teaching comes with a bunch of examples and playgrounds and are available on her website.
This is an example of an image with a shape-outside. The image is already transparent so I don't need to clip it as well. The effect really only comes into play if there is enough text to wrap around some of the shapes, so here is a little bit more text. The image is one I drew as an exercise in using the Apple Pencil in Pixelmator. I wrote a few words on it here.
One fun thing to note is that
shape-outside can be animated! I have a separate lab with CSS animations, so head over there to see an example.
Your browser devtools likely have a WYSIWYG shapes editor that helps make the correct polygon function. Add a basic polygon yourself and then click the shapes editor to get started.