Example of CTools Style Plugin dot inc file.

panesandblocks.inc

<?php
/**
* Defines a style plugin
*
*  - panesandblocks: corresponds to directory name of plugin
*  - render pane: the suffix of the theme function for the pane (without "theme_").
*     - Example: If the function name is "theme_panesandblocks_render_pane",
*       the value of "render pane" is "panesandblocks_render_pane".
*  - render region: the suffix of the theme function for the region (without "theme_").
*     - Example: If the function name is "theme_panesandblocks_render_region",
*       the value of "render region" is "panesandblocks_render_region".
*  - pane settings form: name of function that returns a settings form
*  - hook theme: array of hook theme information
*    - define an array for pane and region. The key must match the first parameter of the returned theme() in the 
*       corresponding theme_ function.
*       Example: 'hook theme' => 'panesandblocks_theme_pane' => array();
*        In function theme_panesandblocks_render_pane:
*          return theme('panesandblocks_theme_pane'...) [truncated]
*      - template: corresponds to name of tpl.php for pane, i.e. panesandblocks-pane.tpl.php
*      - path: the path where the template file lives
*      - variables: an array of variables to add to the $variables array in the theme function
*
*/
$plugin =  array(
  'panesandblocks' => array(
    'title' => t('My Custom Pane Styles'),
    'description'   => t('Simple styles that highlight sections of your page.'),
    'render pane' => 'panesandblocks_render_pane',
    'render region' => 'panesandblocks_render_region',
    'pane settings form' => 'panesandblocks_settings_form',
    'hook theme'    => array(
      'panesandblocks_theme_pane' => array(
        'template' => 'panesandblocks-pane',
         'path' => drupal_get_path('module', 'name_of_module') .'/plugins/styles/panesandblocks',
         'variables' => array(
           'content' => NULL,
           'settings' => NULL,
         ),
       ),
      'panesandblocks_theme_region' => array(
        'template' => 'panesandblocks-region',
         'path' => drupal_get_path('module', 'name_of_module') .'/plugins/styles/panesandblocks',
         'variables' => array(
           'content' => NULL,
         ),
       ),
    ),
  ),
);

function theme_panesandblocks_render_pane($vars) {
  $settings = $vars['settings'];
  $content = $vars['content'];

  return theme('panesandblocks_render_pane', array('content' => $content, 'settings' => $settings));
}

function theme_panesandblocks_render_region($vars) {
    $content = '';

  foreach ($vars['panes'] as $pane_id => $pane_output) {
    $content .= $pane_output;
  }
  if (empty($content)) {
    return;
  } 
  return theme('panesandblocks_render_region', array('content' => $content));
}

function panesandblocks_settings_form($style_settings) {

$options = array(
  'pane-nostyle' => t('Plain / no styles / transparent background'),
  'pane-patterned' => t('Patterned'), 
  'pane-reverse' => t('Reverse color values'), 
  'callout-orange' => t('Callout: Orange'), 
  'callout-blue' => t('Callout: Blue')
);
$headings = array(
  'pane-heading-default' => t('Describe Default Heading Style Here'),
  'pane-heading-secondary' => t('Describe Secondary Heading Style Here'),
  'pane-heading-tertiary' => t('Describe Tertiary Heading Style Here')
);
 
  $form['css_classes'] = array(
    '#type' => 'radios',
    '#title' => t('Custom Pane and Block Styles'),
    '#description' => t('Choose a style for your pane or block.'),
    '#options' => $options,
    '#required' => FALSE,
    '#default_value' => (isset($style_settings['css_classes'])) ? $style_settings['css_classes'] : 'pane-nostyle',
  );

  $form['heading_classes'] = array(
    '#type' => 'radios',
    '#title' => t('Header Styles'),
    '#description' => t('Choose a header style for your pane or block.'),
    '#options' => $headings,
    '#required' => FALSE,
    '#default_value' => (isset($style_settings['heading_classes'])) ? $style_settings['heading_classes'] : '',
  );
  
 
  return $form;
}