The only way to have separate thumbnail and main image pages is to force the gallery to be displayed by the Mobile Player (instead of the Flash Player)  by setting the useFlash Embed Code Parameter (in svBuilder-Pro's 'Customize -> Embed' section) to FALSE.

The Mobile Player (designed as an HTML fallback for mobile devices and browsers which do not have Adobe Flash Player installed and enabled) initially displays a thumbnail page from which a main image can be selected. The main image will replace the thumbnail page and the user can return to the thumbnail page via the Thumbnail Button on the gallery's Button Bar.

Please note that the Mobile Player supports fewer configuration options than the Flash Player.

If you just want thumbnails and no main image at all (in the Flash Player), then you could try setting maxImageWidth="0" and maxImageHeight="0" and frameWidth="0".