Create custom image block style variations.

block-styles-es5.js

wp.domReady( () => {

	wp.blocks.registerBlockStyle( 'core/image', {
		name: 'default',
		label: __( 'Default' ),
		isDefault: true,
	} );

	wp.blocks.registerBlockStyle( 'core/image', {
		name: 'circular-image',
		label: __( 'Circular' ),
		isDefault: false,
	} );

	wp.blocks.registerBlockStyle( 'core/image', {
		name: 'rounded-corners',
		label: __( 'Rounded Corners' ),
		isDefault: false,
	} );

} );