step 1: get a rounded corner image and the image you want to use and use it like this:
Code:
<div class="whatever">
<a href="#"><img src="myroundedimage.png" alt="" /></a>
</div>
then the css
Code:
.whatever{background: transparent url(myimage.jpg) no-repeat;}
of course you'll need different classes for each image (like .whatever, .whatever1, .whatever2 and such)
the same could be accomplished this way:
Code:
<div style="background: transparent url(myimage.jpg) no-repeat;">
<a href="#"><img src="myroundedimage.png" alt="" /></a>
</div>
therefore, you'll need 1 class per image. Using php, you can do it automatically