Multisite and WordPress Featured Images / Post Thumbnails
Post Thumbnail is a theme feature introduced with Version 2.9. Thumbnail is an image that is chosen as the representative image for Posts, Pages or Custom Post Types. The display of this images is up to the theme.
If you’ve added or uploaded a theme to your WP mutisite installation and the “Featured Images” are not showing up, then you need to adjust some of the network wide settings.
To show the “Featured Image” meta box in mulsite installation, make sure you update the allowed upload file types, in Network Admin, Network Admin Settings SubPanel#Upload_Settings, Media upload buttons options. Default is off.
Once that setting is enabled, just add this code to your theme to enable the featured images:
if ( function_exists( 'add_theme_support' ) ) {
add_theme_support( 'post-thumbnails' );
}
