I found the idea for this project at Nutrish.com, although it does not appear to be there any longer. I pinned the picture on my Pinterest page so you can visit there.
I bought a 2 pack of 4×4 canvas from my local craft store. then I drew an outline with pencil. I then filled in either the background or the shape with a permanent marker. In a very few minutes I have a pair of pictures to hang up!
I chose to do cats because cats are my thing and I went with black and white because I had a black marker at home, but I could certainly see doing this with a wide variety of silhouettes and even colors. This project is only limited by your imagination!