I can't get at that link, but I can imagine the effect you are trying to achieve.
Patterns, particularly these hard edge bitmaps, should be used sparingly. Particularly when used behind text. When they are used they are subtle and created in PhotoShop or the like or as vector graphics from programs like Illustrator, then brought into Pages.
There is a very good reason books are not printed on wallpaper. When you do use background images and patterns, designers usually work hard at ensuring a buffer between the two, preferring smooth backgrounds with contrasting colors and tones.
The usual technique is to have a white or black dropshadow to visually lift the text off the textured surface. The text should also be very bold to stand out and be legible. Mostly though it is a questionable technique and does nothing for the design.
I mentioned that it was an old feature, because it dates back to when many monitors were black & white and printers were dot-matrix or B&W laserprinters that could not reproduce even tones or even greys. Really it is a software solution to a problem you wish you didn't have.
Peter