My son and I build scale model airplanes and take pictures of them usually 5-6 per model. I'm looking for an ap that allows editing and arranging the photos. Would like the photos to display a main large shot surrounded by the smaller thumbnail shots. I've looked on iTunes Store and there are so many different ones. Would prefer a free ap but will pay for one if it can suit my needs. It will be used on my ipad2 and iPad mini.