Apply your desired pattern to the wall using painter's tape. Tape works best with patterns that incorporate straight lines, such as stripes, squares and rectangles. For stripes, paint the wall a light base color and allow to dry thoroughly. Use a pencil and a yardstick to mark the stripes on the wall. Set masking tape along the outer edges of the stripes. Paint between the tape to color the stripes. Or make a grid on the wall with masking tape and paint in each square or rectangle with your choice of color.
Use stencils to add patterns on the wall. There are wall stencils available to enable you to paint a pattern on an entire wall. Or you can choose to use a border stencil. Tape the edges of the stencil to the wall with painter's tape. Paint inside the stencil with your desired color. Allow the paint to dry for a few hours before removing the stencil. Place the stencil on the next area and repeat.
Hang wall frame molding. These are four pieces of molding that are nailed together to resemble a picture frame. Paint the molding your desired color. Add some adhesive on the back of the frame at the corners and attach it to the wall with a nail gun. You could also stencil images on the wall inside the frame for an added decorative touch.
Design your own pattern for the wall. Draw your pattern freehand on the wall with pencil to use as a guide. Use small art brushes and enamel paint for a border or larger paintbrushes and acrylic latex paint for patterns that cover the entire wall.