code: public void setImageName(String imageName) {
  		if (imageName.length() == 0) {
  			imageName = null;
  		}
  
  		this.imageName = imageName;
  		if (imageName == null) {
  			image = null;
  		} else {
  			updateImage = true;
  		}
  	}
docs: Set the name of the image to use on a per particle basis. The complete
  reference to the image is required (based on the relative path)
  
  @see #setRelativePath(String)
  
  @param imageName
  The name of the image to use on a per particle reference