Choose hard plastic or acrylic stencils that have a larger rather than smaller design for a patio. The tiny designs won't be visible when you're standing or even sitting. A large design is more noticeable. A simpler design rather than an intricate design is better for the same reason. The details will get lost when viewed from eye-level height. Concrete is a rough surface that makes small, intricate designs come out blurry. Stencils are available in many different themes. Nature-inspired themes work well outside, but also consider geometric patterns.
Create a rug on the patio using tape as the stencil guide and layering the colors. Paint the patio a base color. Arrange painter's tape in rows or crosshatch them in a pleasing pattern. Paint in between the tape. Remove the tape when the paint is dry. Add additional tape patterns and colors until you're satisfied with the look. The smoother the patio, the more defined the pattern will be. If your concrete is rough, the tape won't give you as clean or crisp a definition as a smooth patio.
Most stencils work by applying the paint to the area that is cut out. However, a reverse stencil is painted around a solid figure. Think of it this way. When you make a stencil of ivy, you would cut out the ivy garland from the acrylic. A reverse stencil uses the cut-out ivy garland to prevent the paint from covering underneath it. Using both the cut-out stencil and the solid stencil gives an unusual effect to the patio. Sponge paint in between the two stencils to blend the paint.
Use natural leaves, fruits and flowers as stencils. Flatten the leaves between heavy books for a few days. Paint the concrete your base color. After 24 hours, paint a darker or lighter color on the surface of the leaf and place it on the concrete. Tamp the leaf down so the paint transfers from the leaf to the patio. Studier large leaves such as magnolia, oak or fern work well. One leaf will last through about 10 uses as a stencil. Flat flowers such as gerbera daisies also work well. Paint fruit halves such as lemons, oranges, apples and pears with glaze and press them on the patio.