While it's not something we'll have for 7.3, I have thought on this quite a bit. There are hurdles to overcome, such as if a user belongs to multiple groups that have custom titles.

So, what I think we'll end up with is where the end user can end up choosing what custom title they want to display. If it's just little graphics for each designated title, like we use for admin/mod flags right now, maybe they'll get an option to choose those as well.

So, it's definitely something we'll be getting into our next release.