After a few final attempts to get new volunteers or other forms of help, I decided it is time to put the Drupal Theme Garden to rest; I simply don't have the time and the interest to be its responsible maintainer. And after these attempts (a few mails and requests on the infrastructure and theme developer mailing lists), it seems no one else has that time to spend or is interested in taking over. I posted a longer and in-depth story on my blog about the reasoning behind this action. In short, I have decided to discontinue the Drupal Theme Garden with the release of Drupal 5.0.
Just to be clear: this is not a call for volunteers. However, if you are seriously interested in taking over its maintenance, you must convince the infrastructure people, not me, to make you the new maintainer. In order to do that, you must be really serious and have serious time to spend on it: it makes little sense if someone takes over only to find that he or she loses interest after a month and to find ourselves back where we are right now.
I hope Drupal Theme Garden was of use to you, I hope it convinced some people who were looking for a good CMS that Drupal has decent theming capabilities, and I hope it helped you with your decision to use a contributed theme.