But I lean towards a demo package. Simple, maybe 3 examples. How to make use of CR, just adding content and retrieving. Just like what I have done for ticket-tracker lite and another project of ours. Then example 2, small app that makes use of CR folders. And lastly another app that has revisions.
Actually if the demo package is a bad idea, I would take file-storage as the best candidate. Aside from ETP, it was FS that thought me about CR. And now CMS. Of course if ETP 2 is here then we have an good app to study.