Article: This works best for images that are small and can flow seamlessly into each other. You can use these controls to adjust the spacing between the tiled images, whether or not they're mirrored, and the alignment. This is especially useful if you want to add watermarks to your slides. Setting a background image with a high transparency will allow you to use an image as a watermark without obscuring or distracting from the information on the slides. This menu allow you to select from a variety of different effects that you can apply to your background image. You'll see a preview of each in the menu, as well as the name if you hold your cursor over it.  Click the "Artistic Effects" menu and select the effect you want to use. When you select an effect, additional options may appear beneath it. The options vary depending on the effect you chose. This will change all of the slides in your presentation to use the background image and effects you selected.

What is a summary?
Check the "Tile picture as texture" to turn the image into a tiled texture. Adjust the tiling effect with the controls below. Use the transparency slider to adjust the image transparency. Click the "Effects" button at the top of the "Format Background" menu to apply effects. Click "Apply to All" to apply the effects to all of your slides.