A simple and flexible way to add source of overlapping circular pictures, currently supports horizontal overlapping or distant pictures with great layout flexibility.

onlyPictures.order = .descending

@IBOutlet weak var onlyPictures: OnlyHorizontalPictures!

onlyPictures.dataSource = self
onlyPictures.delegate = self

extension ViewController: OnlyPicturesDataSource {

    // ---------------------------------------------------
    // returns the total no of pictures
    
    func numberOfPictures() -> Int {
        return pictures.count
    }
    
    // ---------------------------------------------------
    // returns the no of pictures should be visible in screen. 
    // In above preview, Left & Right formats are example of visible pictures, if you want pictures to be shown without count, remove this function, it's optional.
    
    func visiblePictures() -> Int {
        return 6
    }
    
    
    // ---------------------------------------------------
    // return the images you want to show. If you have URL's for images, use next function instead of this.
    // use .defaultPicture property to set placeholder image. This only work with local images. for URL's images we provided imageView instance, it's your responsibility to assign placeholder image in it. Check next function.
    // onlyPictures.defaultPicture = #imageLiteral(resourceName: "defaultProfilePicture")
    
    func pictureViews(index: Int) -> UIImage {
        return pictures[index]
    }
    
    
    // ---------------------------------------------------
    // If you do have URLs of images. Use below function to have UIImageView instance and index insted of 'pictureViews(index: Int) -> UIImage'
    // NOTE: It's your resposibility to assign any placeholder image till download & assignment completes.
    // I've used AlamofireImage here for image async downloading, assigning & caching, Use any library to allocate your image from url to imageView.
    
    func pictureViews(_ imageView: UIImageView, index: Int) { 
    
        // Use 'index' to receive specific url from your collection. It's similar to indexPath.row in UITableView.
        let url = URL(string: self.pictures[index])
        
        imageView.image = #imageLiteral(resourceName: "defaultProfilePicture")   // placeholder image
        imageView.af_setImage(withURL: url!)   
    }
}

extension ViewController: OnlyPicturesDelegate {
    
    // ---------------------------------------------------
    // receive an action of selected picture tap index
    
    func pictureView(_ imageView: UIImageView, didSelectAt index: Int) {
        
    }
    
    // ---------------------------------------------------
    // receive an action of tap upon count
    
    func pictureViewCountDidSelect() {
        
    }
    
    // ---------------------------------------------------
    // receive a count, incase you want to do additionally things with it.
    // even if your requirement is to hide count and handle it externally with below fuction, you can hide it using property `isVisibleCount = true`.
    
    func pictureViewCount(value: Int) {
        print("count value: \(value)")
    }
    
    
    // ---------------------------------------------------
    // receive an action, whem tap occures anywhere in OnlyPicture view.
    
    func pictureViewDidSelect() {
        
    }
}

onlyPictures.order = .descending

onlyPictures.recentAt = .left

onlyPictures.alignment = .left

onlyPictures.countPosition = .right

onlyPictures.gap = 36

onlyPictures.spacing = 2

onlyPictures.spacingColor = UIColor.white

onlyPictures.imageInPlaceOfCount = UIImage(named:"image_name")

onlyPictures.backgroundColorForCount = .orange

onlyPictures.textColorForCount = .red

onlyPictures.fontForCount = UIFont(name: "HelveticaNeue", size: 18)!

onlyPictures.isHiddenVisibleCount = true

onlyPictures.insertFirst(image: UIImage(named: "p11"), withAnimation: .popup)

onlyPictures.insertLast(image: UIImage(named: "p12"), withAnimation: .popup)

onlyPictures.insertPicture(UIImage(named: "p12"), atIndex: 2, withAnimation: .popup)

onlyPictures.removeFirst(withAnimation: .popdown)

onlyPictures.removeLast(withAnimation: .popdown)

onlyPictures.removePicture(atIndex: 2, withAnimation: .popdown)

let url = URL(string: "http://insightstobehavior.com/wp-content/uploads/2017/08/testi-5.jpg")
onlyPictures.insertFirst(withAnimation: .popup) { (imageView) in
        imageView.image = #imageLiteral(resourceName: "defaultProfilePicture")
        imageView.af_setImage(withURL: url!)
}

let url = URL(string: "http://insightstobehavior.com/wp-content/uploads/2017/08/testi-5.jpg")
onlyPictures.insertLast(withAnimation: .popup) { (imageView) in
        imageView.image = #imageLiteral(resourceName: "defaultProfilePicture")
        imageView.af_setImage(withURL: url!)
}

let url = URL(string: "http://insightstobehavior.com/wp-content/uploads/2017/08/testi-5.jpg")
onlyPictures.insertPicture(atIndex: 2, withAnimation: .popup) { (imageView) in
        imageView.image = #imageLiteral(resourceName: "defaultProfilePicture")
        imageView.af_setImage(withURL: url!)
}