The most important part of the module, the presets.
They're made of a a key with an array of "actions" to apply
You can put any key you want as long as it works in a URL.
However a recommendation is to put the size of the final image in the preset name,
this allows for much more reusability in your presets. because if you create a rule named "thumbnails"
and that your layout changes the sizes of your thumbnails but only in some places, you'll soon end in a mess with the preset names