If you want to get only the icons URL, you need to copy and paste this function in your functions.php file :

function extract_caticonsurl($string,$return_always_array=FALSE) {
	$myarray = array();
	if (preg_match_all('/<img\s+.*?src=[\"\']?([^\"\' >]*)[\"\']?[^>]*>/i', $string, $matches, PREG_SET_ORDER))  {
		foreach ($matches as $match) {
			$myarray[] = $match[1];
		}
	}
	if ($return_always_array === FALSE && count($myarray) == 1 ) $myarray = array_pop($myarray);
	return $myarray;
}

And paste this code where you want to get the URL(s) :

$caticons_url = extract_caticonsurl(get_cat_icon('echo=false'));

The extract_caticonsurl function returns an array if there’re several icons, or a string (the URL) if there is only one.