if (class_exists('MultiPostThumbnails')) {
new MultiPostThumbnails(array(
'label' => 'Secondary Image',
'id' => 'second-image',
'post_type' => 'project'
));
new MultiPostThumbnails(array(
'label' => 'Tertiary Image',
'id' => 'third-image',
'post_type' => 'project'
));
}
add_image_size('project-second-image-thumbnail', 100, 100);
add_image_size('project-third-image-thumbnail', 100, 100);