Prevent Width and Height Attributes in Image Tag Output

I’m trying to control the output of the random image within this bit of code. The end goal is to NOT output the width and height attributes for the image.

I want this:

<img src="https://wordpress.stackexchange.com/questions/53524/URL HERE" alt="ALT HERE"/>

BUT I DON’T WANT THIS (which is what the code below currently outputs):

<img src="https://wordpress.stackexchange.com/questions/53524/URL HERE" alt="ALT HERE" width="200px" height="200px" />

My code:

$thumb_id = get_post_thumbnail_id(get_the_ID());

$args = array(
    'order' => 'ASC',
    'orderby' => 'rand',
    'post_type' => 'attachment',
    'post_parent' => $post->ID,
    'post_mime_type' => 'image',
    'post_status' => null,
    'numberposts' => 1,
    'exclude' => $thumb_id
);

$attachments = get_posts($args);
if ($attachments) {
    foreach ($attachments as $attachment) {
        echo wp_get_attachment_image($attachment->ID, 'full', false);
    }
}

Use wp_get_attachment_image_src() and build a simplified img element. You may use something like the following code as a replacement for wp_get_attachment_image():

function wpse_53524_get_image_tag( $attach_id, $size, $icon, $alt="" )
{
    if ( $src = wp_get_attachment_image_src( $attach_id, $size, $icon ) )
    {
        return "<img src="https://wordpress.stackexchange.com/questions/53524/{$src[0]}" alt="$alt" />";
    }

}

Put the function above into your theme’s functions.php. Call it like wp_get_attachment_image():

foreach ( $attachments as $attachment ) {
    echo wpse_53524_get_image_tag( $attachment->ID, 'full', false );
}