Here you can set the options for the thumbnails. You may as well force the program to resample the large image (this may be useful for the web - say your images are 2400 x 1600 and you need web-friendly images at 640 x 400).
If the thumbnails link to popup dialogs (the popup contains the large image) you can set up the popup properties, including a background image or color.
Within the
first tab you can choose the images to be inserted (they can link to either a simple page, a popup window, or a given frame).
