Insert the ClipArt which you like to shown as Watermark from Insert - Picture
- Clipart.
Select the Clipart and see if Picture Toolbar appear automatically. If not
than click View - Toolbar - Picture. It could be the second button in this
toolbar name "Color". Choose Washout. You also set the Text Wrapping "Behind
Text" within from same toolbar. Set more brighter and darker the Clipart
using "Contrast" and "Brightness" buttons from the same toolbars.
Hope this information helps you, let us know!