post_thumb to link to its post?

Is this inside the Loop? If so, why are you using $page->ID?

yes this is the whole code actually

<ul>
<?php
$parent = 6;
$args=array(
'child_of' => $parent
);
$pages = get_pages($args);
shuffle($pages);
if ($pages) {
$pageids = array();
foreach ($pages as $page) {
$pageids[]= $page->ID;
}
echo get_the_post_thumbnail($page->ID);
}
?>
</ul>

it is, this is the full code actually:

<ul>
<?php
$parent = 6;
$args=array(
'child_of' => $parent
);
$pages = get_pages($args);
shuffle($pages);
if ($pages) {
$pageids = array();
foreach ($pages as $page) {
$pageids[]= $page->ID;
}
echo get_the_post_thumbnail($page->ID);
}
?>
</ul>

ideally i would like to show the post title of that thumb as well and both the title and the thumb to be a link to its post

How about:

<ul>
<?php
$parent = 6;
$args=array(
	'child_of' => $parent
);
$pages = get_pages($args);
shuffle($pages);
if ($pages) {
	foreach ($pages as $page) :?>
	<li><a href="<?php echo get_page_link($page->ID)"><?php echo $page->post_title; ?> <?php get_the_post_thumbnail($page->ID);?></a></li>
	<?php endforeach;
}
?>
</ul>

did you forget to close any tags? gives me an error ??

Fixed.

$parent = 6;
$args=array(
'child_of' => $parent
);
$pages = get_pages($args);
shuffle($pages);
if ($pages) {
$pageids = array();
foreach ($pages as $page) {
$pageids[]= $page->ID;
$title = get_the_title($page->ID);
$link = get_page_link($page->ID);
}
echo get_the_post_thumbnail($page->ID);
echo "<a href='$link'>$title</a>";
}
?>