You can now create/edit/compile/delete layers. And then they show up when you make styles at:
That's how you test.
Hack away. Make layouts... make themes. Now it's easy for you to contribute! Just go learn S2.
Learn by example by looking at the source (via the layerbrowse page) for the other layouts.
Some formal documentation from mart is currently available here:
Now that S2 is actually available, documentation for it is a bigger priority. I'll announce whenever S2 doc updates are available.
Big disclaimer: This is *not* user-level stuff. This is developer stuff. Users will customize the look from the style editing page, and the "Customize" wizard. They'll never program in S2, or even be aware of its existence.
(Now that all components of S2 are done for FotoBilder, the move to put it on LiveJournal will be pretty straight-forward, and should happen soon, so learning S2 will be beneficial for at least two sites....)
Bug reports and questions welcomed.