TextureFilter

This filter produces a grayscale texture based on the Perlin noise function. You can specify the scale factor of the texture, a stretch factor, an angle of stretch, the amount of noise and the turbulence of the noise. You can also specify a painting mode which allows you to use the texture to modify the source image. To get good effects from this filter, you need to supply a color map.

texture texture texture texture

Other ideas: try blurring or embossing the textures. Layer textures on top of each other by passing an image through the filter more than once with different settings.