Bob's right. You don't specify the toc.png files in the sidecar.xml file. If you add them to the article folders, they're used automatically. Example:
Thanks for that, that explains it all - Sorry I thought the TOC preview would have to be written somewhere into the coded metadata
I didn't realise that they were imported aswell if they were left in the _stack folder
Thanks again Guys
for a lot of pages the standard TOC preview doesn't look great as it takes a snap of a square section of the page, No thank you!!
I want my own!!
Thanks again Bob Bringhurst for expanding and answering my first question!