There are several sites that offer open source web-templates - you can take them and build your own site on them.
You choose one of their templates and turn them into a theme in 20-30 minutes with some experience. So if you watch the recorded presentation you will be able to follow Mark explanations step by step. We will put them online within the next few days.
Additionally there is already a lot of information in the development wiki.
In Mark's presentation you will also learn about the need to still provide table style sheets and how to correctly implement them.
Also a theme isn't only the template for the general layout - with for example the RSS theme you can generate RSS from every templated module. Of course it is also possible to generate other kinds of XML or other ways of displaying content.
One major advantage of the new theme engine is the possibility to completely port a theme with all settings from a sandbox site to the live site as all variables are stored in Smarty compatible .ini files.
We hope that this presentation sparks a new wave of themes and inspires new people to design their own layouts as these steps do not only apply to open Source web templates but also for your own designs created in Dreamweaver, NVU and so on. Mark already converted more than 100 free web templates that are available for .8 in the NOC or on Mark West's homepage.
BTW: Some more photos