Small change to Wordpress plugin Categories Images.Use thumbnails, rather than full-size images, on category listing page in WP admin.

Wordpress plugin Categories Images

/**
 * Thumbnail column value added to category admin.
 *
 * @access public
 * @param mixed $columns
 * @param mixed $column
 * @param mixed $id
 * @return void
 */
function z_taxonomy_column( $columns, $column, $id ) {
	if ( $column == 'thumb' )
		$columns = '<span><img src="' . z_taxonomy_image_url($id, 'thumbnail', TRUE) . '" alt="' . __('Thumbnail', 'zci') . '" class="wp-post-image" /></span>';
	
	return $columns;
}