I too noticed the appearance of these default group icons in the forums. In my own case, I didn't see any need for these icons, so I went to users, groups, edit group settings, and switched the "hide" dropdown (see below.)
Sure, I can see that sometimes it might be good to have group icons, so this by itself didn't bother me. Yes, I agree that the icons should all be on the top line, right justified. Of course, it is possible for a student to belong to 50 groups, and icon management can get a little wild, but if the icons were on the top line (as in moodle.org), sure, this would be better. I will vote on a feature request if someone cares to start one.
There are two things that have caught my attention and are bothersome.
1) This setting to Hide icons only occurs after the group is created. Sometimes I create 5 to 10 groups "automatically." If I want to hide the icon, I then have to edit 10 groups. I would recommend that this "Hide" feature be available on the Auto-create Groups web setup page. Comments, please.
2) Even when I turn the icons to off, they appear strangely when selecting a Forum. In my attached picture, I am hiding icons for each group, but look at how a "no" icon shows. Isn't this strange? Comments, please.
And I still would like to see a group designation show somewhere when I am actually into a discussion. This is my own MDL-58043