By clicking on the object image you can choose the 3D object you want to use.
You can select following 3D objects:
BoxShot
CD
DVD Case
Screenshot
Member Card
Book

Background color of the output image. In the dropdown palette you can select one of predefined colors or select own color using "More Colors.." button.
In order to create an image with transparent background, please select a "Transparent" color.
Background color is used only if you have no background image.

Dragging color picker image you can select background color from any place on the screen.

Settings of the currently selected 3D Object. These settings are different for different types of 3D objects.