So the group information page is the top level of a decision tree - and the banner picture helps to confirm that a member or administrator has come to the correct group ...
Good point. Last night I noticed that while looking at the archive, settings or other group pages the identity of the group is not displayed anywhere, save the browser address bar.
I don't know that we need the cover image on all pages, as Yahoo Groups Neo does, but I think the group name and title ought to be showing somewhere in the header area.
