faceA <- function(x, y, width, height) {
  pushViewport(viewport(x=x, y=y, 
                        width=width, height=height))
  grid.rect() 
  grid.circle(x=c(0.25, 0.75), y=0.75, r=0.1)
  grid.lines(x=c(0.33, 0.67), y=0.25) 
  popViewport()
}

faceB <- function(x, y, width, height) {
  pushViewport(viewport(x=x, y=y, 
                        width=width, height=height))
  grid.draw(rectGrob()) 
  grid.draw(circleGrob(x=c(0.25, 0.75), y=0.75, r=0.1))
  grid.draw(linesGrob(x=c(0.33, 0.67), y=0.25)) 
  popViewport()
}