Storage Info

New Sites—Although new Sites is included with Drive, your sites, and the content you embed in them, doesn’t count toward your Drive storage quota.

The above comment came from Google's support page. It has been changed. Please note that content that you store in Drive and then embed in a site does take up Drive space.

Learn more about Drive storage space.

Photos and other content added to a site is stored within that site (it's not added to Drive or any other Google products). Deleting a Site file also deletes the content within that site. Separate copies stored in Drive are not affected.