Do you have a different image on each individual chapter header page?
The TOC shoud be grabbing that image (it needs to be placed in the placeholder frame, the one that is there with the template)
also you can place a different image in the TOC for each chapter then what is in the chapter header page.
is the TOC loading the images that are on each chapter page? (do't place the images on the TOC page, place them on the cahpter pages.
if that is not working then the link has been broken or there is no "main" image placeholder on each chapter page.
You can test to see how it works with a new document.
If it is working properly, then you can relace the images on the TOC page (after you place the images on the individual chapter header pages.
There are some old threads with screen captures etc.
Its a very simple solution:
Click on the slightly grey holding box for the TOC image, make sure that is selected and not one of the text boxes.
locate the image you want, and hit enter.
This image will only appear in one TOC background.
For the next chapter click the appropriarte little dot below and repeat the above.