Extends the [gallery] shortcode to be able to create galleries from image taxonomies or the featured images of specific Posts.
There are a few reasons:
You would need to register a custom taxonomy for attachments/images or you could just use the PhotoPress - Image Taxonomies plugin.
If you are using the taxonomy and term shortcode params, then your galleries will no longer display images. If you are using the caption_source param then WordPress wil revert to using the excerpt as the source of the cpation text. if You are using the post_type param then your gallery will no longer display images.