custom field thumbs / featured images

ORIGINAL FROM REVOLUTION LIVESTYLE

                <?php if( get_post_meta($post->ID, "thumbnail", true) ): ?>
                    <a href="<?php the_permalink() ?>" rel="bookmark"><img style="float:left;margin:0px 10px 0px 0px;" src="<?php echo get_post_meta($post->ID, "thumbnail", true); ?>" alt="<?php the_title(); ?>" /></a>
                <?php else: ?>
                    <a href="<?php the_permalink() ?>" rel="bookmark"><img style="float:left;margin:0px 10px 0px 0px;"  src="<?php bloginfo('template_url'); ?>/images/thumbnail.png" alt="<?php the_title(); ?>" /></a>
                <?php endif; ?>


EDITED VERSION

                <?php if( get_post_meta($post->ID, "thumbnail", true) ): ?>
                    <a href="<?php the_permalink() ?>" rel="bookmark"><img style="float:left;margin:0px 10px 0px 0px;" src="<?php echo get_post_meta($post->ID, "thumbnail", true); ?>" alt="<?php the_title(); ?>" /></a>

<?php elseif(get_the_post_thumbnail($post->ID)) : ?>
                    <a href="<?php the_permalink() ?>" rel="bookmark"><?php the_post_thumbnail(); ?></a>

                <?php else: ?>
                    <a href="<?php the_permalink() ?>" rel="bookmark"><img style="float:left;margin:0px 10px 0px 0px;"  src="<?php bloginfo('template_url'); ?>/images/thumbnail.png" alt="<?php the_title(); ?>" /></a>
                <?php endif; ?>

THAT IS THE GENERAL IDEA:
a: check for the custom field images - if there - use theme (old posts);
b: check for featured images - if there - use them (new posts);
c: show default;

similar for the 'hpbottom' ones;

you probably need to adapt this to your edits so far;
and you probably need to fill a few parameter into the thumbnail codes:

http://codex.wordpress.org/Function_Reference/get_the_post_thumbnail
http://codex.wordpress.org/Function_Reference/the_post_thumbnail