Definitely iframes is the worst possible route you could take here!

You'll just need to run a loop with query_posts, should be pretty easy. Something like this:

<?php query_posts('post_type=page&post_parent=####'); ?>
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
	<a href="<?php the_permalink(); ?>"><?php the_post_thumbnail(); ?></a>
<?php endwhile; ?>
	<!-- post navigation -->
<?php else: ?>
	<!-- no posts found -->
<?php endif; ?>
<?php wp_reset_query(); ?>

Where '####' is the ID of the parent page (probably the portfolio page?).

Well, presumably all of your images are going to be the same size, so you could just wrap a div around them like this:

<div class="grid-item"><a href="<?php the_permalink(); ?>"><?php the_post_thumbnail(); ?></a></div>

And then float them all to the left. Apply appropriate margins, etc.

Hey Doc, I've implemented what you recommended but it is only pulling the image from the slider I have configured for the homepage. I have since disabled the slider on the homepage but it is only pulling that slider image which is itself another page.

This is where I am testing out the grid if you would like to have a look.

http://studio7.greenflagseo.com/pages-grid/

Thanks!

I actually used your code and fixed some stuff on my page, and your code works perfect. All set, thank you!