As gasparuff says, you can also do it with a UIButton, just set the images:
[button setImage:[UIImage imageNamed:@"image_on"] forState:UIControlStateSelected];
[button setImage:[UIImage imageNamed:@"image_off"] forState:UIControlStateNormal];
and when it's tapped just toggle the selected property.
- (void) buttonTap {
button.selected = !button.selected;
}
Which will change the images automatically.