You could teach phrasal verbs and the sequence of verbs. I have a worksheet that shows how you sometimes can use two tenses for the same thing: http://www.eslprintables.com/grammar_worksheets/verbs/verb_tenses/simple_past/At_Grandpa_s_House_Used_to_w_629502/#thetop
 
Another option is YouTube lectures and so on, especially TedTalks. I made up a worksheet for a couple online videos: http://www.eslprintables.com/printable.asp?id=815440#thetop
 
You can also teach various registers of language. Look up the Five Clocks of English. I made a worksheet introducing the topic: http://www.eslprintables.com/speaking_worksheets/conversation/Introducing_Formal_Informal_La_636714/#thetop
 
You might also teach them language by functions, so that they can see how many different ways there are of saying the same thing: 
  http://www.lancs.ac.uk/fass/projects/stylistics/contents.htm
 
http://www.indiana.edu/~discprag/spch_acts.html 
http://carla.umn.edu/speechacts/descriptions.html
 
    
  acceding to a request
  agreeing/disagreeing
  apologizing
  approving
  asking for a favor
  asking for help
  asking for information (personal or otherwise)
  asking for instructions or help
  bargaining
  being imprecise or vague
  contrasting ideas
  criticizing
  demanding explanations
  describing actions
  describing experiences
  describing habits/routines
  discussing interests and hobbies
  enquiring (about prices or features of a product, etc.)
  expressing a personal point of view
  expressing a wish
  expressing cause and result
  expressing likes/dislikes
  giving advice
  giving information
  giving instructions
  giving warning
  greetings
  guessing
  making complaints
  making suggestions
  making suggestions/proposing
  naming
  offering (help, etc.)
  ordering
  persuading
  promising
  refusing
  reminding
  requesting
  saying �no� nicely
  showing preferences
  stating position/destination
  sympathizing
  talking about the past
  threatening
    In a pinch, you can go to BBC English or RealEnglish. Though they claim to be beginning and intermediate, frequently, real language is more advanced. 
http://www.bbc.co.uk/learningenglish/
http://www.real-english.com/