I believe I've fixed the 'sorting issue'. It seems that when we upgraded some of our core files, this difference you saw was hardcoded within the upgrade rather than being a option.
As for the thumbnails, these can be used by the 'group creator' to help describe the group they've created. Like an avatar for your group.
Here are some of the improvements made to social groups:
* Social Group Discussion Topics
While the previous 'social group messages' system allows messages to be posted to a social group, unlike forums it did not allow messages to be divided up into discussions. Being one of the most requested features, social groups in 3.8 now have the ability to contain individual topics, each with reporting, inline moderation and many of the other tools one would expect.
* Social Group Avatars
In the new version, when users create a social group, they can upload a picture to represent the group, which will be shown both on the group page, and on the list of groups.
* Social Group Categories
To help users to find more easily a social group that they’d like to join, the administrator can now create categories to which social groups can belong.
Let me know if you have any other concerns, thanks!