Select the slide whose layout you want to change.

Choose View > Show Inspector, and then click the Slide inspector button.

Click Appearance.

To add a title box or other elements to the slide, use the checkboxes below the master slide thumbnail image.

To apply a background, choose a background type from the Background pop-up menu.

• Color Fill:  
  Makes the background a single, solid color. Click the color well and choose a color in the Colors window.
• Gradient Fill:  
  Colors the background with a color gradient. Click each color well and choose colors in the Colors window.
• Image Fill:  
  Uses your own image as a background. Click Choose and select an image.
• Tinted Image Fill:  
  Uses your own image with a semiopaque color tint over it. Click Choose and select an image.

If you chose Image Fill or Tinted Image Fill, choose a scaling option from the pop-up menu. See Filling an Object with an Image for more information.