Make uploaded image thumbnail bigger
Here's want you need to do to modified the image field thumbnail thats display after you upload an image.

You will need to overwrite the imagefield_widget_preview theme function. You can drop this theme overwrite in the template.php file of your theme.

function THEMENANE_imagefield_widget_preview($item = NULL) {
  //By default this returns  theme('imagefield_admin_thumbnail', $item);
  //But If you're going to change it I would recommend replacing it with image-cache.
  //Also you should keep the imagefield-preview div.
  return '&lt;div class="imagefield-preview"&gt;' . theme('imagecache', 'your_custom_preset', $item['filepath'], $item['alt'], $item['title']) . '&lt;/div&gt;';
}


This will replace the thumbnail images uploaded using image field.

Hope this helps.

Also remember, to use the name of the theme thats being used when editing. In-case you're using different themes.