Hide certain thumbnail sizes from media uploader in Wordpress
<?php
function remove_image_size_95344($possible_sizes) {
unset( $possible_sizes['small'] );
unset( $possible_sizes['medium'] );
unset( $possible_sizes['large'] );
return $possible_sizes;
}
add_filter('image_size_names_choose', 'remove_image_size_95344');
?>