You could assign something like " (Closed dd/mm/yyyy)" to the end of the matter name (if the matter is closed) when you update it from your PMS, maybe using ndLink, to make it clear to users. Maybe you could also add the area of law/practice area to the end of the matter name.
You could also use the area of law/practice group as the matter type, then setup a different workspace template for each matter type, setting the Description on the template to e.g. "Corporate", depending on the type of matter.
Hope this helps.