Another more simple implementation may be to use a UIImageView as a parent view, then add a UIImageView as a subview for any images you wish to overlay on top of the original.
let mainImage = UIImage(named:"main-pic")
let overlayImage = UIImage(named:"overlay")
var mainImageView = UIImageView(image:mainImage)
var overlayImageView = UIImageView(image:overlayImage)
self.view.addSubview(mainImageView)
mainImageview.addSubview(overlayImageView)
Edit: Since this has become the accepted answer, I feel it is worth mentioning that there are also different options for positioning the overlayImageView: you can add the overlay to the same parent after the first view has been added, or you can add the overlay as a subview of the main imageView as the example demonstrates.
The difference is the frame of reference when setting the coordinates for your overlay frame: whether you want them to have the same coordinate space, or whether you want the overlay coordinates to be relative to the main image rather than the parent.