After Defining an image as a pattern you can shift the pattern by holding down the shift key and dragging with the grabber tool. It's best to start with a larger size and resolution and then scale down. For smooth blending of colors use jpeg format instead of gif.
Text looks better in the gif format.
The Opacity of a drop shadow can be changed long after creation. Simply select only the shadow from the floater list and change to the desired color and opacity. You can also distort the shadow when selected like this to give greater depth.