In Thailand, Buddhist monks bless businesses by making designs on the walls or ceiling using powder and small squares of paper-thin gold leaf. In shops, the drawings are usually found near the sign on the storefront, and in taxis, you can see the creations on the ceiling. The designs vary, but are generally made up of white dots, lines and swirls along with a few symmetrically-placed gold squares. The designs look like a Thai temple or Buddha's head and are meant to represent Buddha's enlightenment. They're intended to bring good luck and good fortune to business owners, and in the case of the taxis, the designs are meant to protect and help the driver, the passengers, and the car itself.
Sometimes in businesses, the monk drawings are small. But, in some taxis, half the ceiling is covered in white powder and gold. I asked my taxi driver the other day if the size of the monk drawing affects the potency or the meaning in any way, and the cabby told me it doesn't make much difference, and that it's up to the monk's creativity and mood. Some of those monks can get pretty artistic.