I recently downloaded QuadCamera, which is an app that takes 4 to 8 continuous shots and groups them into one photo.
I decided to use my cat Onion as my first model, because he's so good looking. I wasn't thrilled with the low contrast of the particular setting I used, so I took it through three stages and two different apps to get the picture I wanted.
First, I set QuadCamera to a 2-second timer, a 2x2 layout, and grayscale setting with Shadow set to "on".
Second, I opened the above photo in the PS Express app and increased the contrast, because I wanted a fairly stark image.
Third, while still in PS Express, I went into Effects, chose Vignette Blur, and voilà!