There should be truly internationalized content support for the automatically translated screenshots. Currently it can only pick internationalized UI, but not content that the user "typed".
It can probably be stored in the usual JSON i18n files translatable in translatewiki.
Change 224965 had a related patch set uploaded (by Amire80):
[BrowserTest] Add true internationalized content support to language screenshot
Change 224965 merged by jenkins-bot:
[BrowserTest] Add true internationalized content support to language screenshot
What is the status of this task, now that Wikimania 2015 is over? Did this hacking project take place and was successfully finished? If yes: Please provide an update and potentially summarize findings / provide a link to anything relevant (and if the task is not completely finished yet, please move the project to the "Work continues after Mexico City" column on the #Wikimania-Hackathon-2015 workboard). If no: Please edit this task by removing the #Wikimania-Hackathon-2015 project from this task. Thanks for your help and keeping this task updated!
Basic support is done by Vikas, further work will be done in the coming weeks. Thanks!