Description
bool 
imagesettile ( resource image, resource tile )
     imagesettile() sets the tile image to be
     used by all region filling functions (such as imagefill()
     and imagefilledpolygon()) when filling with the special
     color IMG_COLOR_TILED.
    
     A tile is an image used to fill an area with a repeated pattern. Any
     GD image can be used as a tile, and by setting the transparent color index of the tile
     image with imagecolortransparent(), a tile allows certain parts
     of the underlying area to shine through can be created.
    
Note: 
      You need not take special action when you are finished with a tile, but if you
      destroy the tile image, you must not use the IMG_COLOR_TILED 
      color until you have set a new tile image!