Those textures seem random and very evenly distributed.
closed as off topic by Philip Regan Aug 11 '11 at 11:39
Questions on Graphic Design Stack Exchange are expected to relate to graphic design within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.
The basic technique is to create a background color or gradient, add a 50% Grey layer above it with its blend mode set to "Overlay" and add some noise to that layer using whatever method your program provides. In Photoshop it's a filter, and I seem to recall it's much the same in the gimp. Adjust the amount of noise (which should be monochromatic) and opacity to suit.