This repository is a storage location for stock-theme thumbnails originally hosted on Vyond. If you'd like to know about how I did it, I got the item IDs by running a quick Powershell script to perform regex-search on the theme files. The original file URLs were obtained with the following PowerShell script:
Select-String -Path ../ga-w/themes/*.xml -Pattern 'https://s3.amazonaws\.com/fs\.goanimate\.com/files/.{1,90}\.(?:png|jpg)' -AllMatches | % {$_.Matches.Value}