How to dynamically add css after image upload on node?
If you use drupal behaviors to modify the css, it should run after the ajax too.

eg.

(function ($) {
  Drupal.behaviors.exampleModule = {
    attach: function (context, settings) {
      $('.example', context).css('backgroud-color', '#ff0000');
    }
  };
})(jQuery);


More info at: http://drupal.org/node/756722