I’d like to have a different image appear as the thumbnail for each portfolio item than the image that appears at the top of the featured media list. Ideally the thumbnail image would not appear at all when a user clicks through to view the portfolio items, but it would be okay if the thumbnail image was the last one on the featured media list.
Go to Choices > Theme Options > Layout & Settings and scroll down to the “Slideshow behavior on overview pages” option. Select “Display only single image on overview pages and all slideshow images except the first on single entries” by using the dropdown box. By going this way the first image will be used for the thumbnail, all other images for the slideshow.