Ahhh.. gotcha. I see where that's a problem, and not one that anyone's mentioned before, actually. To fix, edit the /modules/mod_sclogin/helper.php file. Find the function getJFBCConnectButton() function. In there, replace the following line:
$buttonHtml .= '<fb:login-button v="2" onlogin="javascript:jfbc.login.on_login();">' . JText::_('MOD_SCLOGIN_CONNECT_BUTTON') .'</fb:login-button>';With:
$buttonHtml .= '<a href="javascript:void(0)" onclick="jfbc.login.login_custom();"><img src="/link-to-your-image.jpg" /></a>';
You can use the same image as in the parameters, or a different re-connect image.
I've taken this as a bug in our feature tracker. Hopefully we can make it, at least, use the same image as the login button in an upcoming version.
Hope that helps!
Alex