Homepage Custom Post Thumbnail

have you tried this one?
http://www.press75.com/the-simple-post-thumbnails-wordpress-plugin/

You can also add them using a custom field on the post and adding a line of code to your index.php file. If you would like to see some possible code to use, post the lines of code from your theme’s homepage file from the start of the WP loop through the display of the_content or the_excerpt (it will be one or the other, the_content or the_excerpt)
like this

<?php while (have_posts()) : the_post(); ?>
   <div <?php post_class() ?> id="post-<?php the_ID(); ?>">
      <h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
      <small><?php the_time('F jS, Y') ?> <!-- by <?php the_author() ?> --></small>
      <div class="entry">
         <?php the_content('Read the rest of this entry &raquo;'); ?>
      </div>