Simple Code Completion Project [SWIFT 3] : populate CollectionView from folder images

I have dragged a folder "pictures" from Finder into my xcode project as a folder reference not a group. I have placed three images only inside it just for a demonstration and later on, i will add more than 100 images. I have created an empty array "var picturesArray = [UIImages]()". [1] i want to populate the array by looping though images in "pictures" folder and NOT to be added manually one by one. [2] I already placed a collectionView controller and added an imageView inside the prototype cell. I want to populate this collectionView from the images inside the array, populated above. I have tried to do this myself but i keep getting this error "Could not load the image referenced from a nib in the bundle with identifier.