Snippets → WordPress
Remove unneeded thumbnails
Adding some or all of these lines of code to the functions.php of your wordpress theme will effectively remove some of the default images sizes that may be unneeded.
update_option( 'thumbnail_size_h', 0 ); update_option( 'thumbnail_size_w', 0 ); update_option( 'medium_size_h', 0 ); update_option( 'medium_size_w', 0 ); update_option( 'large_size_h', 0 ); update_option( 'large_size_w', 0 );
Source: http://wpsnipp.com/index.php/functions-php/remove-unneeded-i...