You can make variations of the texture.
In the ToolPalette, click the category of texture you are interested in, then click one of the texture icons to the right.
Now, click the Variations button on the ToolPalette.
In the Variations dialog box, select a preview and click the Variation button to create a new mutation derived from the preview selected. Now, you can select another preview and make a new variation again.
Now generate the texture. Apply preview selected texture to the image. You can select another preview and repeat generate if necessary or click the Parameters button for modify the texture setting.
After a little while (the rightmost portion of the status bar shows the progress), the rendered texture will be displayed.