There are many improvements that I hope to see with group management in the future, but for now I would love to see some group icon diversity. At the moment a single different icon (the leader crown) really isn't that helpful. In fact I find that many groups don't even use that icon for the person leading the group; since it's the only one that looks different.
I would love to see the option to allow players to select an icon for group members or even use the icon that is used for their selected role. Though this wouldn't help the upcoming console players, even opening it up the the add-on community would help immensely.
Really anything to help me quickly find a dead healer among 5 other dead players, or even having multiple leader icons for a large group.