Here’s a quick tip that’s very easy to implement. When new sites are created with WordPress Multisite, the default behavior is to assign the WordPress TwentyTen Theme.
However, if you’d like to use a different theme, you can add the WP_DEFAULT_THEME constant definition to wp-config.php file, like so:
Replace ‘classic’ in the example above with the theme name that you want to define as the default.
Setting a default theme is very important, if you intend to remove the TwentyTen theme completely, according to the codex:
If you do remove the WordPress TwentyTen theme then you need to define a new default theme with the WP_DEFAULT_THEME constant. Disabling a theme in the Network Admin Themes Screen does not prevent that theme being used by a site. It only prevents the theme being listed in the available themes list when selecting a new/different theme.
In other words, setting the constant will keep your new sites from being assigned the TwentyTen theme.
How to Create a Template for New Site Signups on WordPress Multisite
Now, if you want to take this a few steps further and create an entire new site template for your new signups, you can use the New Blog Templates plugin. It allows you to define templates that include not only the default theme, but default active plugins, WordPress settings, posts, pages, categories, tags, links, and users.
The New Blog Templates plugin allows you to create as many templates as you like for use when adding new sites through the Network Admin dashboard. These will save you quite a bit of time if you’ve got an active network where you’re constantly setting up new sites for students, classes, stores, professionals, personal websites, or however you’re putting multisite to work for you. Lastly, you can assign any of your blog templates as the default so that new signups will be automatically given the right template when they use your signup form.
Unless you want your network to use the default TwentyTen theme for all new signups, it’s going to take a bit of effort up front. These tips should make it much easier for you to expand your multisite network while automating the assignment of the default theme for your new sites.