post thumbnails only on category archive page

To stop them from showing on full posts you can use this CSS:

.single .page-header-image-single {
    display: none;
}

Thanks Tom,
I can hide them just fine once they're there. I can't figure out how to get the thumbnail on the archive in the first place.

Tom, I got it. User error ;)

I had removed the featured image while tinkering.

Thanks for the help!

No problem! :)