EDIT - This tutorial is now outdated. I'll update it with new images when I have time.
To find thumb codes now: 1. Go to deviation 2. Find the blue words "Share" under the deviation 3. Copy the code under "Thumb"
Now that thumb codes are usable for everyone, I hope that this tutorial will be helpful for some people, especially since I do get an endless plethora of questions on my status stamps about how to use stamps...even though the directions are already in the description. :'D
I made this mostly for the directions in Ooo look another thumbnail! *shot*