Ahhh... well there are quite a few
"now playing" plugins, for different services, but you never indicated which particular one you are using, or what service you are using it with.
In any event, for an answer to your question, you'll either have to consult the documentation that may/may not have been provided, or ask your question of the author of the specific plugin you are using to find out whether or not other parameters can be used.
You posted yet again as I was typing my reply. So, now that you have
identified the plugin
, you need to contact either Antti or Lauri Nevala (the authors), to find out whether or not other parameters can be used.