We just published the first WPGlobus extension (add-on), WPGlobus Featured Images.
The WPGlobus Featured Images plugin does not require any additional settings. The only thing you will notice after you install and activate it is the new multilingual metabox for the featured image. The standard WordPress metabox will be hidden, and the new one will show language tabs, with separate images in them.
If you do not set a featured image for one of the languages, the image will be taken from the default language tab.
Do not forget to make sure that your WordPress theme supports featured images for posts.