Using setAttrib() to set class for Image Element dose not render to html (class="") however this method works for other form elements.

Also the helper in the Image attributes is formText. Shouldn't that be formImage?

$image = new Zend_Form_Element_Image('submitImage');
$image->setLabel('')
            ->setValue('image.gif')
            ->setAttrib('class', 'button')
            ->setAttrib('foo', 'bar');

var_dump($image->getAttribs());

Outputs: array(3) { ["helper"]=> string(8) "formText" ["class"]=> string(6) "button" ["foo"]=> string(3) "bar" }

HTML:

This behavior is with Zend_Form_Element_Image and not with any other (Text, Textarea, etc.), these all render the attrib to html.