Another simple but dramatic way to incorporate textures into your creative projects is to stamp with or impress objects into your colors, pastes and gels. The action of pressing into a wet material will also create a bit of randomness in how your shape appears...as you release your object or stamp, your acrylic medium will left with varying peaks from where it clung to the stamp/object. Here are a couple examples:
Above is a board made with a "fossil-like" effect using a feather impressed into wet Molding Paste (that was applied first with a palette knife). When the Molding Paste was dry, it was then embellished with color.
This second example involved using a stamp, but the material (Fiber Paste) was applied directly to the stamp, giving the stamped paste a more refined edge. After the Fiber Paste was dry, color was added to the whole surface. Due to its absorbency, the Fiber Paste surface was treated with a fluid acrylic wash to really amplify its fibrous texture.