The default TOC page in iBA shows an image placeholder on the right which covers 50% of the page. Drop an image if you choose. On teh left is blank space or your particular Chpater and section information. IF you decide to stetch an image to vover teh whole page... it may clash with teh text and it may puch the text back layer and appear lost, Use ARRANGE - Bring to Front.
On your Mac using iBooks Author, the TOC shows at the bootom a black footer with a slider and white dost as does the iPad. Each "dot" represents a Chapter and you will see - IF - you have added sections, a line which - example - shows for Chapter 10.. the Chapter and title you gave it, 2 sections would show as:
10.1 Test 1
10.2 Test 2
These become links in your book - but do not work on your mac/iBA - they do work on your iPad or iBooks on Mac.
You do not get pages listed... in iBooks, you see a line of page thumbs to select your choice of Chapter, Section Pag
Viewing a book using iBooks is visual. The printed book "Index" or TOC is not neccasary