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/