Correct markup for Image Galleries?

I'm working on a site that hosts many images.  The site's basic page
architecture is two-level: gallery pages displaying a themed set of images,
each with a thumbnail of the image and a link to a dedicated page with a
full size version of the image.

Working through the schema.org markup for this, I have a couple of
questions.

Is ImageGallery an appropriate type for the gallery pages?

Is it appropriate to mark up each thumbnail on the gallery page as an
ImageObject?  If yes, should these ImageObjects be embedded within the
ImageGallery?  My first instinct was that the answer to both of these
questions is yes, but it's not apparent that there is a suitable property
on ImageGallery for this.  The primaryImageOfPage - by its name and
description - seems to suggest that it represents a single image that is
the main subject of the page (indeed, this description makes it sound like
ImageGallery is the appropriate type for the individual image pages, not
the collection).  What is the correct way to represent such a collection?

Thanks for any guidance.

John