This is one of the recent technique that I've used in my latest layout titled "Fun" in my family gallery. I've tried to blend the photograph with the it's background card stock.
This technique is actually quite simple. Simply use a dry paint brush and dab it into some acrylic paint directly from the bottle and lightly swipe it on the edges of the photograph. It's also creating a distressing effect to the photograph as well. I love this effect and I will definitely use this technique again in some of my future layout.