Theme management has also changed drastically in 1.10. Here's a basic rundown of how it works:

To install a new theme, go to the Themes tab of your admin Settings. Click on "Add Theme". You'll need to enter a name, and you can optionally add a description and a thumbnail. If "Default" is checked, you will immediately switch to the new theme once it's uploaded.

Theme files zip should be a zip archive containing two folders: templates/ and static/. These contain your theme's templates and static files, respectively. Your templates will be loaded normally with Django's template loader; your static files can be accessed by using the {% static %} template tag provided by {% load uploadtemplate %}.

It's important to manage your themes so that you don't get overwhelmed (and to improve the efficiency of your site). If there is a theme that you're not using, you should delete it.