EDIT

<?php

/**

 * Provides the image names which can be configured in the theme settings to all

 * theme setting functions.

 *

 * @return multitype:string

 *     the list of image names which can be configured in the theme settings

 */

function _zen_dataportal_imagenames() {

  static $image_list = array('banner', 'body_background', 'page_background');

  return $image_list;

}

/**

 * Implements hook_form_system_theme_settings_alter().

 *

 * @param $form

 *   Nested array of form elements that comprise the form.

 * @param $form_state

 *   A keyed array containing the current state of the form.

 */

function zen_dataportal_form_system_theme_settings_alter(&$form, &$form_state, $form_id = NULL)  {

  // Work-around for a core bug affecting admin themes. See issue #943212.

  if (isset($form_id)) {

    return;

  }

  $form['zen_dataportal_colors'] = array(

          '#type' => 'fieldset',

          '#title' => t('Colors'),

          '#description' => t('Configure colors where.'),

          '#attributes' => array('class' => array('theme-settings-bottom')),

  );

  $form['zen_dataportal_colors']['site_name_color'] = array(

      '#type'          => 'textfield',

      '#title'         => t('Site name color'),

      '#default_value' => theme_get_setting('site_name_color'),

      '#description'   => t('Set the color of the site name which is shown in the header. Must be a css color value like: #000000'),

  );

  //

  // custom images for banner, body and page backgrounds

  //

  foreach(_zen_dataportal_imagenames() as $which_image) {

    zen_dataportal_form_widget_image($form, $which_image);

  }

  $form['#validate'][] = 'zen_dataportal_theme_settings_validate';

  $form['#submit'][] = 'zen_dataportal_theme_settings_submit';

  // We are editing the $form in place, so we don't need to return anything.

}

/**

 * Process zen_dataportal admin form submissions.

 * @param $form

 *   Nested array of form elements that comprise the form.

 * @param $form_state

 *   A keyed array containing the current state of the form.

 */

function zen_dataportal_theme_settings_submit($form, &$form_state) {

  foreach(_zen_dataportal_imagenames() as $which_image) {

    zen_dataportal_form_widget_image_submit($form_state, $which_image);

  }

  // update logo information like wich one to use and size, this is needed to

  // offset the banner and menu bar

  $values = &$form_state['values'];

  if(!theme_get_setting('default_logo')) {

    $logo_file = path_to_theme() . '/logo.png';

  } else {

    $logo_file = theme_get_setting('logo_path');

  }

  $logo_file_info = image_get_info($logo_file);

  if(isset($logo_file_info['width'])) {

   $values['logo_size'] = array('width' => $logo_file_info['width'], 'height' => $logo_file_info['height']);

  }

  /*

   * Ok, we are done here the $values will be saved in the theme

   * variable by system_theme_settings_submit($form, &$form_state)

   * in modules/system/system.admin.inc

   */

}

/**

 * Validator for the system_theme_settings() form.

 *  @param $form

 *   Nested array of form elements that comprise the form.

 * @param $form_state

 *   A keyed array containing the current state of the form.

 */

function zen_dataportal_theme_settings_validate($form, &$form_state) {

  foreach(_zen_dataportal_imagenames() as $which_image) {

    zen_dataportal_form_widget_image_validate($form_state, $which_image);

  }

}

/*******************************************************************

 *                    form widget functions

 *******************************************************************/

/**

 *

 * Enter description here ...

 *  @param $form

 *   Nested array of form elements that comprise the form.

 * @param unknown_type $which_image

 */

function zen_dataportal_form_widget_image(&$form, $which_image){

  $image_label = str_replace('_', ' ', $which_image);

  $form['zen_dataportal_' .  $which_image] = array(

          '#type' => 'fieldset',

          '#title' => ucfirst(t($image_label)) . ' ' . t('image settings'),

          '#description' => t('If toggled on, the following image will be displayed.'),

          '#attributes' => array('class' => array('theme-settings-bottom')),

  );

  $form['zen_dataportal_' .  $which_image]['default_' . $which_image] = array(

          '#type' => 'checkbox',

          '#title' => t('Use the default') . t($which_image),

          '#default_value' => theme_get_setting('default_' . $which_image),

          '#tree' => FALSE,

          '#description' => t('Check here if you want the theme to use the image supplied with it.')

  );

  $form['zen_dataportal_' .  $which_image]['settings'] = array(

          '#type' => 'container',

          '#states' => array(

            // Hide the logo settings when using the default logo.

            'invisible' => array(

              'input[name="default_' . $which_image . '"]' => array('checked' => TRUE),

            ),

          ),

  );

  // If $path is a public:// URI, display the path relative to the files

  // directory; stream wrappers are not end-user friendly.

  $path = theme_get_setting($which_image . '_path');

  $image = '';

  if (file_uri_scheme($path) == 'public') {

    $url = file_create_url($path);

    $path = file_uri_target($path);

    $form['zen_dataportal_' .  $which_image]['settings'][$which_image . '_preview'] = array(

          	'#type' => 'item',

            '#title' => t('Preview'),

            '#markup' => '<div class="image-preview"><img src="' . $url . '"/></div>',

    );

  } // FIXME manully entered files without scheme public: are omitted here

  $form['zen_dataportal_' .  $which_image]['settings'][$which_image . '_path'] = array(

          '#type' => 'textfield',

          '#title' => t('Path to custom') . ' ' . t($image_label),

          '#description' => t('The path to the file you would like to use as your') . ' ' . t($image_label),

          '#default_value' => $path,

  );

  $form['zen_dataportal_' .  $which_image]['settings'][$which_image . '_upload'] = array(

          '#type' => 'file',

          '#title' => t('Upload') . ' ' . t($image_label) . t(' image'),

          '#maxlength' => 40,

          '#description' => t("If you don't have direct file access to the server, use this field to upload your image.")

  );

}

/**

 *

 * Enter description here ...

 * @param $form_state

 *   A keyed array containing the current state of the form.

 * @param unknown_type $which_image

 */

function zen_dataportal_form_widget_image_submit(&$form_state, $which_image){

  // If the user uploaded a new image, save it to a permanent location

  // and use it in place of the default theme-provided file.

  $values = &$form_state['values'];

  if ($file = $values[$which_image . '_upload']) {

    unset($values[$which_image . '_upload']);

    $filename = file_unmanaged_copy($file->uri);

    $values['default_' .$which_image ] = 0;

    $values[$which_image . '_path'] = $filename;

    $values['toggle_' . $which_image] = 1;

  }

  if (!empty($values[$which_image . '_path'])) {

    $values[$which_image . '_path'] = _system_theme_settings_validate_path($values[$which_image . '_path']);

  }

}

/**

*

* Enter description here ...

 * @param $form_state

 *   A keyed array containing the current state of the form.

* @param unknown_type $which_image

*/

function zen_dataportal_form_widget_image_validate(&$form_state, $which_image){

  $validators = array('file_validate_is_image' => array('gif', 'jpg', 'png'));

  // Check for a new uploaded logo.

  $file = file_save_upload($which_image . '_upload', $validators);

  if (isset($file)) {

    // File upload was attempted.

    if ($file) {

      // Put the temporary file in form_values so we can save it on submit.

      $form_state['values'][$which_image . '_upload'] = $file;

    }

    else {

      // File upload failed.

      form_set_error($which_image . '_upload', t('The image could not be uploaded.'));

    }

  }

}