I do what you're trying to do, using the method Tony mentioned above. In my case I use a product image, so the code below includes a category id and a product id so you can click the image to go to the product. After that, one of my large images is referenced. But you could just code in your own image and ignore the HREF part if you don't want to use the image as a link.
Code:
<div class="home-img">
<a href="http://www.YOUR-SITE.com/index.php?main_page=product_info&cPath=80_95&products_id=456"><img src="images/large/IMAGE-NAME.jpg" alt="" title="" border="0" /></a>
<h4 class="center">SOME TEXT HERE IF NEEDED</h4>
</div>
Put one or two <br /> tags above and below the image to space it out. Also, notice I coded in a DIV with a class name. That makes it possible for me to style the image. I mainly use that to make sure it centers in the space available, but there's lots of things you could do with that.
Rob