There is a word for the publisher's logo at the bottom of the title page and on the spine of a book, but I can't recall it.
That would be called "the Publisher's Logo." Perhaps you are referring to the material which describes who designed the book; the publisher's data; the materials used in its production [etc]. This is called "the colophon."
Added: "Publisher's Mark" is an alternative for "Logo"
Colophon: In publishing, a colophon is a brief statement containing information about the publication of a book such as the place of publication, the publisher, and the date of publication. A colophon may also be emblematic or pictorial in nature.