Get the default image for a profile2 image field with code
You don't need to bother with the field_get_default_value function, you can use the field_info_field function. For image fields, it will provide the fid for the default image in ['settings']['default_image']. 

Suppose your field is "field_picture", then this will get you the fid and file:

$info = field_info_field('field_picture');
if (!empty($info) &amp;&amp; $info['settings']['default_image'] &gt; 0) {
    $default_img_fid  = $info['settings']['default_image'];
    $default_img_file = file_load($default_img_fid);
}