If you have some images like this:

let firstImage = UIImage(named: "first")
let secondImage = UIImage(named: "first")
let thirdImage = UIImage(named: "first")

How to display these images on UIImageView and it change image automatically?

Easy, try this:

let imageView = UIImageView()
imageView.animationImages = [firstImage, secondImage, thirdImage]
imageView.startAnimating()

So how to set number of loops?

imageView.animationRepeatCount = 0 // 0 means infinite (default is 0)

Hummm, ok so how to change velocity?

imageView.animationDuration = 0.5 // 0.5 seconds  for one cycle of images

Now stop it!

imageView.stopAnimating()

Fun, right?, cheers!