I'm having an English conversation class tomorrow and I'm a bit uncreative at the moment.

Any bold suggestions what I should do with them?

Average Age 60 years
Basic to Medium English as foreign language competence.

Ask them to discuss the art of Salvador Dali, with images. Just get them talking about his work, the way it is formed and what messages they feel it expresses.

Edit:::
Five really good paintings (subjectively):
http://en.wikipedia.org/wiki/Swans_Reflecting_Elephants
http://en.wikipedia.org/wiki/The_Sacrament_of_the_Last_Supper
http://en.wikipedia.org/wiki/The_Persistence_of_Memory
http://en.wikipedia.org/wiki/Dream_Caused_by_the_Flight_of_a_Bee_Around_a_Pomegranate_a_Second_Before_Awakening
http://thedali.org/exhibits/highlights/geopoliticus_child_watching_the_birth_of_the_new_man.php

Travel, work and daily life in europe post world war 2.
My dad was stationed in Germany at the time doing his national service - quite an interesting era.
It should cover the basic - intermediate requirements of conversation and allow some reminsience / nostalgia as a lot of folks that age enjoy.
Should also not bore the pants offa you too!