Width

This specifies how wide your form will be. The default “regular” width is 600px, but the dropdown also includes thin (400px450px) and wide (800px). You also may pick the custom option; this will enable the box to the right of the Width dropdown and let you specify your own width.

...

You can choose a theme to alter the appearance of your form. Live Forms   provides two global themes : Clear Nouveau or Professional BlueNouveau Blue. The Clear theme Nouveau theme gives your form a clear (white) background and a submit and the Professional Blue cancel button with rounded corners. The Nouveau Blue has the same characteristics of the Nouveau theme and gives your form a soft blue background. New forms are created with the Nouveau theme.

Of course, you may [[V4_Customizing_Themes | create a custom theme]] instead  instead of using the default themes. After you have added the customized them it will appear in the dropdown list along with the pre-defined options.

...