I spent a few minutes today and knocked up a Confluence space that demonstrates all of the basic rendering functionality. Headlines, lists, images, tables, etc. Why would I do that, you ask? Well, for the benefit of our tiny horde of theme developers. The idea is that one can import this space into Confluence, and quickly test a theme over all the basic functionality just by clicking on a dozen pages.
You’ll find the download attached to this page. And feel free to add new markup and content. The more use-cases we have in there, the better future themes will be.

Resource for theme developers