Poster Pin allows you to scatter and pin different images in your scene: posters, notes, polaroids, and doodles. It will place the pictures onto a wall with tape, pins, and strings, and then you can adjust them for a more realistic feel. You can control the size of the images, how flat they lay on the surface, and how their shadows look.
Once the main focal points are on the wall, you can make it look busier by scattering smaller notes and photos between the bigger ones. Plus, if you choose to place a photo string on the wall, the add-on will let you control the positioning of the thread itself and the pictures hanging off it.