Hi Mike,
Currently, there's no way to do this via parameters. You'll have to hack the code to achieve this.
Open wordpress-popular-posts.php using an editor such as Windows' Notepad or Adobe Dreamweaver, and change this (around line 690):
// get thumbnail
if ($instance['thumbnail']['active'] && $this->thumb ) {
$tbWidth = $instance['thumbnail']['width'];
$tbHeight = $instance['thumbnail']['height'];
// default image
$thumb = "<a href=\"".get_permalink($wppost->ID)."\" class=\"wppnothumb\" title=\"". $title_attr ."\"><img src=\"". $this->pluginDir . "/no_thumb.jpg\" alt=\"".$title_attr."\" border=\"0\" class=\"wpp-thumbnail\" width=\"".$tbWidth."\" height=\"".$tbHeight."\" "."/></a>";
// let's try to retrieve the post thumbnail!
if ($instance['thumbnail']['thumb_selection'] == "usergenerated") { // use thumbnail selected by user
if (function_exists('get_the_post_thumbnail') && has_post_thumbnail( $wppost->ID )) {
$thumb = "<a href=\"".get_permalink($wppost->ID)."\" title=\"". $title_attr ."\">" . get_the_post_thumbnail($wppost->ID, array($tbWidth), array('class' => 'wpp-thumbnail', 'alt' => $title_attr, 'title' => $title_attr) ) ."</a> <!-- $tbWidth $tbHeight-->";
}
} else if ($instance['thumbnail']['thumb_selection'] == "wppgenerated") { // WordPress Popular Posts should attempt to create a thumbnail by itself
$img = $this->get_img($wppost->ID);
if ( ($img && !empty($img)) ) {
$thumb = "<a href=\"".get_permalink($wppost->ID)."\" class=\"wppgen\" title=\"". $title_attr ."\"><img src=\"". $this->pluginDir . "/scripts/timthumb.php?src=". $img[1] ."&h=".$tbHeight."&w=".$tbWidth."&zc=1\" alt=\"".$title_attr."\" border=\"0\" class=\"wpp-thumbnail\" width=\"".$tbWidth."\" height=\"".$tbHeight."\" "."/></a>";
}
}
}
... into this:
// get thumbnail
if ($instance['thumbnail']['active'] && $this->thumb ) {
$tbWidth = $instance['thumbnail']['width'];
$tbHeight = $instance['thumbnail']['height'];
// default image
$thumb = "<img src=\"". $this->pluginDir . "/no_thumb.jpg\" alt=\"".$title_attr."\" border=\"0\" class=\"wpp-thumbnail\" width=\"".$tbWidth."\" height=\"".$tbHeight."\" "."/>";
// let's try to retrieve the post thumbnail!
if ($instance['thumbnail']['thumb_selection'] == "usergenerated") { // use thumbnail selected by user
if (function_exists('get_the_post_thumbnail') && has_post_thumbnail( $wppost->ID )) {
$thumb = get_the_post_thumbnail($wppost->ID, array($tbWidth), array('class' => 'wpp-thumbnail', 'alt' => $title_attr, 'title' => $title_attr) );
}
} else if ($instance['thumbnail']['thumb_selection'] == "wppgenerated") { // WordPress Popular Posts should attempt to create a thumbnail by itself
$img = $this->get_img($wppost->ID);
if ( ($img && !empty($img)) ) {
$thumb = "<img src=\"". $this->pluginDir . "/scripts/timthumb.php?src=". $img[1] ."&h=".$tbHeight."&w=".$tbWidth."&zc=1\" alt=\"".$title_attr."\" border=\"0\" class=\"wpp-thumbnail\" width=\"".$tbWidth."\" height=\"".$tbHeight."\" "."/>";
}
}
}
That should do the trick.