Zend framework form Decorators
<form action="/index/login" method="post" id="login_form">
        <div class="input_row">
            <img src="/images/user_icon.png" class="login_icon" alt=""/>
            <label for="username" class="login_label">Username:</label>
            <input type="text" name="username" value="" id="username" class="login_input"  />
        </div>
        <div class="input_row">
            <img src="/images/password_icon.png" class="login_icon" alt=""/>
            <label for="password" class="login_label">Password:</label>
            <input type="password" name="password" value="" id="password" class="login_input"  />
        </div>
        <div class="input_row">
            <input type="submit" name="login_submit" value="Login" class="login_submit"  />
        </div>
    </form>

$form = new Zend_Form;

    $form->setAction('/index/login')
         ->setMethod('post')
         ->setAttrib('id', 'login_form');

    $username = $form->createElement('text', 'username');
    $username->addValidator('alnum')
             ->setRequired(TRUE)
             ->setLabel('Username')
             ->setAttrib('class', 'login_input');


    $username->setDecorators(array(
            'ViewHelper',
            'Errors',
            array('Label',array('class' => 'login_label')),
            array('row' => 'HtmlTag'), array('tag' => 'div', 'class' => 'input_row')
        ));


    $form->addElement($username)
         ->addElement('submit', 'login', array('label' => 'Login'));

$form = new Zend_Form;

    $form->removeDecorator('htmlTag');

    $form->setAction('/index/login')
            ->setMethod('post')
            ->setAttrib('id', 'login_form');

    $username = $form->createElement('text', 'username');

    $username->addValidator('alnum')
            ->setRequired(TRUE)
            ->setLabel('Username')
            ->setAttrib('class', 'login_input');


    // anonymous function that will generate your image tag
    $makeImg = function($content, $element, array $options) {
                return '<img src="/images/' . $options['img'] . '" class="' . $options['class'] . ' " alt=""/> ';
            };


    $username->setDecorators(array(
        'ViewHelper',
        'Errors',
        array('Label', array('class' => 'login_label')),
        array('Callback',
            array(
                'callback' => $makeImg,
                'img' => 'user_icon.png',
                'class' => 'login_icon',
                'placement' => 'PREPEND'
            )
        ),
        array('HtmlTag', array('tag' => null, 'class' => 'input_row')),
    ));

    $form->addElement($username);


    $submit = $form->createElement('submit', 'login', array(
                'label' => 'Login',
                'class' => 'login_submit'
                    )
    );


    $submit->setDecorators(array(
        'ViewHelper',
        'Errors',
        array('HtmlTag', array('tag' => null, 'class' => 'input_row')),
    ));

    $form->addElement($submit);

<form id="login_form" enctype="application/x-www-form-urlencoded" action="/index/login" method="post">
      <div class="input_row">
         <img src="/images/user_icon.png" class="login_icon " alt="">
         <label for="username" class="login_label required">Username</label>
         <input type="text" name="username" id="username" value="" class="login_input">
      </div>
      <div class="input_row">
         <input type="submit" name="login" id="login" value="Login" class="login_submit">
      </div>
   </form>