Displaying Sub Categories and their description on a template page.

Some code like this should work:

<?php $parent_id = 8; // The ID of the parent category
$rows = get_categories("include=$parent_id");
$cat_name = $rows[0]->name;
$rows = get_categories("child_of=$parent_id&hide_empty=0");
echo "<h2>Subcategories of $cat_name</h2>";
foreach ($rows as $row) {
  echo "<p>Name: {$row->name}<br />Description: {$row->description}</p>";
}
echo '<br />';
?>

Hi Maning84,

Check the below link
http://en.support.wordpress.com/images/

Step 1:
go to admin

Step 2:
post image in particular category and subcategory as mentioned in above link

Step 3:
display the image where you want

Also,check the below links for further reference
http://codex.wordpress.org/Using_Images
http://codex.wordpress.org/Using_Image_and_File_Attachments

Cheers!

Senthil