echo $this->Html->image("recipes/6.jpg", array(
    "alt" => "Brownies",
    'url' => array('controller' => 'recipes', 'action' => 'view', 6)
));

<a href="/recipes/view/6">
    <img src="/img/recipes/6.jpg" alt="Brownies" />
</a>

<a href="/recipes/view/6" class='picture'>
    <img src="/img/recipes/6.jpg" alt="Brownies" />
</a>

<?php echo $this->Html->link(
$this->Html->image("loading.gif", array('alt' => 'Brownies', 'border' => '0')),
array('controller' => 'recipes', 'action' => 'view', 6),  array('class' => 'picture', 'escape' => false));

echo $this->Html->link(
    $this->Html->image("recipes/6.jpg", array('alt' => 'Brownies')),
    array('controller' => 'recipes', 'action' => 'view', 6, array('escape'=>false', 'class'=>'picture')
);