Im not sure how wordpress passes in its categories but you could put something along the lines of this in your template
Code:
<?
$category = $_GET[category]; //not sure about this part, might need to explode(); the url and use the last value in the array, as i said i dont know how this is put together in wordpress exactly.
if($category == 'anal') { echo "html code for anal banner"; }
elseif($category == 'ebony') { echo "html code for ebony"; }
else { echo "no matches, generic banner html"; }
?>