You can log in with Username: User and Paswword: Password . Note that there is limited fucntionality for this account but it is enough for you to Demo the templates. If you want to Demo JomSocial, you can visit jomsocial.com .
would be nice to have a jomsocial theme with a real DIFFERENT layout. right now all available jomsocial themes look nearly the same - ok, the colours change ^^ why not have a complete different style like facebook or others... perhaps you can come up with something? ;)