This is really quite simple with Drupal 7.
With render and hide you know have the posibility to control the placement of a single element in $content without having to print out all the items yourself like was needed in Drupal 6.
A simplified node template looks like this:
<div>
<h2><?php print $title; ?></h2>
<div class="content">
<?php print render($content); ?>
</div>
</div>
A little modification would handle your needs:
<div>
<?php print render($content['field_name_of_image']); ?>
<h2><?php print $title; ?></h2>
<div class="content">
<?php print render($content); ?>
</div>
</div>
Using render, you can output an element. This is more clever than simply printing stuff, as Drupal will keep track of what has been rendered, to avoid the same thing being printed twice on the place. When rendering the field above the title you are also removing for what's rendered when $content is rendered.
