I'm currently considering to do free themes as well, but my current plan is to at least start with very few really high quality paid themes. But we'll see how much time is left before XenForo goes final.
The great thing about the potential here with regards to styling is that the best style I seen on another platform is that good colour usage by the styler can create beautiful styles. Get the colours right, consistent and flowing in perfect harmony will definitely produce some stunning styles.
I myself will be providing some free styles when the resources area is put in place.
Back to that preview snippet. Nice work. I'm betting that we will see some awesome styles, great colour usage even from the less experienced users. It'll be that easy and with minimal effort.