Two of the images we have from the original thread on /b/, and have an interesting non random string of characters at the start of each image when opened with a hex edtior: "456789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz"

In the IRC chat, lexus_ suggested that the characters that are missing are a key.  The missing characters are "1230:ABKLMNOPQRabklmnopqr".  Please feel free to mess with the order of the caps and lowercase characters and numerals when the time comes for us to use a key.