Photo by Designaglow
This does look like it would be a touch on the tricky side to get the photos into this shape (I would strongly suggest cutting out shapes in brown paper to represent the individual frames and sticking these on the wall first before you put the first photo nail in!) but so worth it for the final result.
Photo from IDA Interior Lifestyle
Here's a relatively simple one from Hobby Craft that you can do yourself. (Just follow the link beneath the pictures for the full "how-to" instructions if you are interested).
Photo from HobbyCraft
And even easier version - stick polariods on the wall!
Photo from Apartment Therapy
And if you are a bit of a crafty type these heart garlands might do the trick. I've seen a couple of now and think they are pretty cute but not sure I would have the patience to give it a go!
Photo from Scrapper Girl
And a couple more for luck...
Photo from kojodesigns.blogspot.com
Photo from carolynshomework.blogspot.com
Photo by Jennifer Lee Weddings