Hey Tom,
in order to enable the tall background slider, two things needed to be done: checking the “Display custom header” box on the “Header Elements” tab of the Theme Options panel; and choosing “background slider” as the custom header on the front page by going to the page editor screen and using the drop-down in the “Custom header” box. I’ve also switched from the NextGen gallery to a folder location in the “Slides Source” tab of the “Appearance -> Background slider” admin menu – but that was just to re-enable the background images. More information and screenshots on how to set up the background slider are available on pages 5 and 6 of the theme manual.
Should you have more questions, do not hesitate to ask!
Sincerely,
Andrew / Satori Studio