Need a little explaining..

[n00dles101]

The way I'd do this is.

o - install my customfields and pages plugins (shameless plug I know )
o - Add a custom field and call it "image"
o - Create your base page - call it 'portfolio' and leave it blank.
o - Now create each of your pages and make the parent "portfolio"
o - add the following function to your themes functions.php

Code:

function getPortfolio(){
    $subpages=getChildren('portfolio');
    foreach ($subpages as $page){
        $title=returnPageField($page,'title');
$image=returnPageField($page,'image');
        echo '<li>';
        echo "<a href='index.php?id=".$page."'><img src='".$image."' alt='".$title."' /></a><br/>";
        echo "</li>";
    }    
}

o - then in your main template just call "getPortfolio();" where you want to display the list of images....

Hope it helps....

Mike

Plugins are here:
http://get-simple.info/extend/plugin/customfields/22/
http://get-simple.info/extend/plugin/page-caching/65/