I see more and more articles and talk about language as if it's 'words' or 'vocabulary'. Language is made up of words in use, in the way we interact socially and as part of our behaviour. Words are not 'language' until they are linked together in 'syntax', with invisible links, that don't announce themselves as 'syntax'.
Bearing this in mind, in addition to your 'wow words' wall, why not create a wall where people can contribute expressions, quotes from songs, overheard bits of conversation on buses, funny notices, misprints in newspapers, witty headlines and shop names, poignant lines from plays or novels, famous sayings or quotes that say something that people think are important.
You could have a couple of 'editors' who 'moderate' the contributions. This could involve a discussion about what it means to moderate and why it's become necessary.
Every so often have discussions about all these quotes and examples of clever or interesting or odd examples of 'language in use', or use any of them as starting points for writing. This is what writers have done for hundreds of years...collect other people's examples of writing and use them as starting points for new writing.
