Here's a quick tutorial on how I did it...
You'll need a strip of Shrinky Dink material, Staz-On, 1/4" circle punch, corner rounder, tweezers or something to hold the Shrinky Dink down, Sharpie Markers, a piece of Parchment paper, a heat tool, and of course the wheel.
Wheel the image onto the rough side of the Shrinky Dink.
Color your image in with the Sharpies on the rough side. I left the sky and windows uncolored. Cut your piece of Shrinky Dink (about the size of a credit card). Round the corners and add a 1/4" hole in one end.
Now's the fun part! Start shrinking! Use the heat gun 3-4 inches above the Shrinky Dink and watch it crinkle.
And crinkle some more!
It will start to flatten out. Keep heating. Until it gets really flat. You may need to flip the Shrinky Dink over to get it to flatten out.
Careful not to get too close with the heat gun. You can see here that my big building looks like it is on fire! Oops! It has character! :) It will look and feel like a gel. Let is sit for a few minutes to harden. If you touch it too soon you risk burning yourself, and causing it to lose it's shape.
And here you go! Add a ring and your key, and you are ready to go! If you want to use more SU! items - you can use a piece of Hodgepodge Hardware in lieu of the ring!