When you use PhoneGap Build Hydra, the ChildBrowser looks in the assets/www folder for the childbrowser folder and it's images Hydra, however, downloads the files separately and stores them in a different directory. When it runs, you just get three small boxes, that are thankfully clickable.
Thanks for the report - please forward this on to the phonegap/build repo (I'm no longer an employee of Adobe, so I don't handle anything related to PhoneGap Build).
When you use PhoneGap Build Hydra, the ChildBrowser looks in the assets/www folder for the childbrowser folder and it's images Hydra, however, downloads the files separately and stores them in a different directory. When it runs, you just get three small boxes, that are thankfully clickable.