I ran into this same problem myself and came up with a solution.

Open up your modules\\mod_muscol_jwplayer\\mod_muscol_jwplayer.xml and add after line 57,

You then should be able to go into your module manager and that field will now show up. You can then type in any text your template has predefined for styling or create some yourself.

EDIT: The code I placed within the code tags gets stripped out. Appears to be a bug with the forums. I will paste the code below outside of the code tags and hope it keeps its correct formatting:

EDIT2: The forums keep stripping out my code. Here is a link to a forum that has the same code posted. Its the post by a user named miga link:

http://forum.joomla.org/viewtopic.php?p=1122205&sid=cc8445093cdc3b78fd3f0fd03231db5b#p1122205

Thank you, it's simply and works