willRenderCanvas to alter the appearance of the image preview, for example, to overlay a circular crop guide.
willRenderToolbar property can be used to add controls to the main toolbar.
willRenderShapeControls properties is used to add or remove controls from shape popup menu.
cropWillRenderTools to adjust the toolbar contents of the crop interface.
resizeWillRenderFooter to adjust the footer of the resize plugin.
The finetune, frame, and filter plugin each have properties to control which options show in their footers. Additionally it's possible to set up custom finetune controls, frames, and filters.