I have solved using a files comparison software.
Just added those customizations.
In the file "skitter.min.jquery.js" at line 833 added this two rows:
...
'fade',
'fadeFour',
...
at line 906 added this (after the break point of "animationTube" function):
...
case 'fade' :
this.animationFade();
break;
case 'fadeFour' :
this.animationFadeFour();
break;
...
and in modules/mod_jfslideshow/fields/slideoption.php file, found the "$transition2_options" row, and added this two rows:
...
JHTML::_('select.option', 'fade', JText::_('fade') ),
JHTML::_('select.option', 'fadeFour', JText::_('fadeFour') ),
...
That's all, thank you