In iOS 8, Apple added the Photos library which makes for easier querying.
import UIKit
import Photos
struct LastPhotoRetriever {
    func queryLastPhoto(resizeTo size: CGSize?, queryCallback: (UIImage? -> Void)) {
        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
//        fetchOptions.fetchLimit = 1 // This is available in iOS 9.
        if let fetchResult = PHAsset.fetchAssetsWithMediaType(PHAssetMediaType.Image, options: fetchOptions) {
            if let asset = fetchResult.firstObject as? PHAsset {
                let manager = PHImageManager.defaultManager()
                // If you already know how you want to resize, 
                // great, otherwise, use full-size.
                let targetSize = size == nil ? CGSize(width: asset.pixelWidth, height: asset.pixelHeight) : size!
                // I arbitrarily chose AspectFit here. AspectFill is 
                // also available.
                manager.requestImageForAsset(asset,
                    targetSize: targetSize,
                    contentMode: .AspectFit,
                    options: nil,
                    resultHandler: { image, info in
                    queryCallback(image)
                })
            }
        }
    }
}