CSS isn't going to be able to call other elements like that, you'll need to use JavaScript to reach beyond a child or sibling selector.
You could try something like this:
.hover_img a { position:relative; }
.hover_img a span { position:absolute; display:none; z-index:99; }
.hover_img a:hover span { display:block; }Then,<div class="hover_img">
<a href="#">Show Image<span><img src="images/01.png" alt="image" height="100" /></span></a>
</div>