How can I stop specific html tags in description?

Is there a way of preventing members from using HTML tags like <img> in their profiles only?

Try the following:

Edit inc/utils.inc.php file by adding the following (near ~626 line):

if (defined('BX_PROFILE_PAGE')) $oConfig->set('HTML.ForbiddenElements', array('img'));
$oConfig->set('HTML.SafeObject', 'true');
$oConfig->set('Output.FlashCompat', 'true');