Eu criei um pequeno projeto de amostra usando o Swift. Eu criei um "MyCustomView" como xib, que contém rótulo, botão e imageView, como mostrado no código abaixo:

import UIKit

@IBDesignable class MyCustomView: UIView {

    @IBOutlet weak var lblName: UILabel!
    @IBOutlet weak var btnClick: UIButton!
    @IBOutlet weak var myImageView: UIImageView!

    var view:UIView!

    @IBInspectable
    var mytitleLabelText: String? {
        get {
            return lblName.text
        }
        set(mytitleLabelText) {
            lblName.text = mytitleLabelText
        }
    }

    @IBInspectable
    var myCustomImage:UIImage? {
        get {
            return myImageView.image
        }
        set(myCustomImage) {
            myImageView.image = myCustomImage
        }
    }


    override init(frame : CGRect)
    {
        super.init(frame: frame)
        xibSetup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        xibSetup()
    }


    func xibSetup()
    {
        view = loadViewFromNib()
        view.frame = self.bounds

        // not sure about this ?
        view.autoresizingMask = [UIViewAutoresizing.FlexibleWidth, UIViewAutoresizing.FlexibleHeight]
        addSubview(view)
    }


    func loadViewFromNib() -> UIView {

        let bundle = NSBundle(forClass: self.dynamicType)
        let nib = UINib(nibName: "MyCustomView", bundle: bundle)
        let view = nib.instantiateWithOwner(self, options: nil)[0] as! UIView

        return view
    }
}

Anexou a imagem do xib para a referência.

No StoryBoard -> ViewController, foi adicionado o UIViewCollection, que é mostrado na imagem abaixo. Nesta coleção, preciso que a célula de cor laranja contenha meu xib personalizado para ser carregado no tempo de execução.

Como faço para conseguir isso?

Novo código modificado, conforme sugerido por Sandeep

// 1 importação de UIKit

class ViewController: UIViewController {

    @IBOutlet weak var collectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.collectionView.register(UINib(nibName: "MyCustomView", bundle: nil), forCellWithReuseIdentifier: "myCell")

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 7
    }

    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return 1
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

        let cell : MyCustomView = collectionView.dequeueReusableCellWithReuseIdentifier("your_reusable_identifier", forIndexPath: indexPath) as! MyCustomView

        cell.lblName.text = "MyNewName"
        return cell
    }
}

// 2 importar UIKit

@IBDesignable class MyCustomView: UICollectionViewCell {

    @IBOutlet weak var lblName: UILabel!
    @IBOutlet weak var btnClick: UIButton!
    @IBOutlet weak var myImageView: UIImageView!

    var view:UIView!

    @IBInspectable
    var mytitleLabelText: String? {
        get {
            return lblName.text
        }
        set(mytitleLabelText) {
            lblName.text = mytitleLabelText
        }
    }

    @IBInspectable
    var myCustomImage:UIImage? {
        get {
            return myImageView.image
        }
        set(myCustomImage) {
            myImageView.image = myCustomImage
        }
    }

}