this is gallery post type – we recommend usage of custom meta for gallery images selection, although you can use native WP gallery, but then more advanced controls are not
Image post format
NASHVILLE FLOWER MARKET | WHOLESALE FLOWERS | WEDDING FLOWERS
To use image post format simply choose featured image in “Featured image” default custom meta box (on he right hand side)
Too long, don’t read: Sometimes one just doesn’t need any “featured post image”, but does want to use some images in post, say – galleries. So this is the example