Place your rug face side up on a floor where the rug can sit undisturbed for at least 24 hours.
Measure 3 inches from each outside edge and tape with painter's tape parallel to the sides of the rug. Measure 6 inches from each outside edge and tape again. You will paint between the sections of tape, so make sure they are pressed down and the corners are straight and clean.
Draw designs on plain paper such as a fleur de lis or a star or other designs you like. Make the design around 8 inches wide and tall. When you like the size and shape of the design, cut it out with scissors. Trace the cut out design on the back side of adhesive shelf paper. Cut out the inside mirror image of the design. You will use the adhesive paper like a big piece of tape.
Center your design at one corner of the rug, remove the backing paper and stick the shelf paper to the rug. Paint the design using acrylic paints or spray paints. (If you use spray paints, cover the rest of the rug and surroundings with plastic sheeting.) Remove the paper and move it to each corner and repeat so that all the corner designs are painted. Now paint your border lines in the area between the two rows of painter's tape. Use a square brush and brush away from the tape. Allow the paint 24 hours to dry before removing the tape.