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.
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
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"