Definition
Frontispiece
A frontispiece is an illustration facing the title page, on the verso opposite. It is the one image many otherwise text-only books carry.
The position is the definition: an image anywhere else in the front matter is a plate, not a frontispiece. Traditionally it was a portrait of the author or a scene from the work, printed on the back of the half-title. Two practical notes for print-on-demand: the image must clear the gutter of a facing spread, and a full-bleed frontispiece has to be built with bleed on all outer edges or it will be trimmed with a white sliver.
Related tools & guides
Front matter, chapter openers and scene breaks, set for you
Ceeryo generates the half-title, title and copyright pages, opens chapters on the right-hand page with the running head suppressed, and turns your blank lines and '* * *' into scene breaks — from the manuscript as you wrote it.