The Droste effect is when a photo recursively appears within itself — the photo within the photo within the photo, “tunneling” forever. Here’s a 12-minute video by photographer and retoucher Antti Karppinen that shows you can create a Droste effect photo for yourself.
But if you want to get a little more crazy, you can use a neat piece of software called Photo Spiralysis.
Karpinnen wanted to use a Droste effect where the image spiraled, rather than simply repeated. The web application uses Safari and allows you to import the image you want to work on.
Once you’ve inserted the image, you can select the shapes you want to work with. Then you have to match the corners of the repeated image into the black frame, and you can see the application making the Droste effect come to life as you do it.
With some tweaking and experimentation, you can come up with some really cool final effects. Here is Karpinnen’s final shot: