oh.. you found bug in a core
public_html/admin/controller/pages/extension/extensions.php line 408
there hardcode of type
array('type' => 'image',
as solution i can propose to you use custom setting tpl (look into default_pp_pro config.xml)
<custom_settings_template>pages/extension/default_pp_pro_settings.tpl</custom_settings_template>
inside your own tpl you can set all html-elements what you want including RL
p.s. do not forget to add this tpl into main.php