So, suddenly, instead of 2 themes for download, you have ~65 (although of course, most of them are bootswatch variations in 2 themes, jinja-default looks exactly like default, and orphan is useless ;-)
And you can contribute themes now!
Give me a pull request at https://github.com/getnikola/nikola-themes
All you have to do is add your theme in themes/ and pull request.
Send me a zip of your theme and I'll do it.
Contributing themes will take a while because the theme has to be examined for malicious code in the templates, but I will process them, slowly but surely. If you have sent me a theme in the past and I have not done it, I am terribly sorry and hope you can find it in you to try one more time :-)
The themes site itself is not exactly awesome, but it is functional, and you can get themes from there too, and see demo sites for each theme, and even look at autogenerated screenshots (which sadly don't show webfonts)