Making NSCollectionView work with nscollectionviewitems that are not all alike

I want my nscollectionviewitems to contain n no. of images where n can be known at runtime.

For eg. my first item contains one image 
second contains 3 images
third again contains 1 image.

Is it possible to have it implemented thru NSCollectionView or do i have to go forward with some custom view.
I am emphasizing on NSCollectionView because I want the subviews to reflow like the way they do in NSCollectionView.

If i have to implement a custom view of my own then how to do that ?