Possibly maclean, though there are many different types of terrorist with different causes. It is only recently that everyone has become obsessed with one type in particular.
The game could perhaps have differing types of terrorists with differing targeting strategies, resources or other abilities depending on their ideology. Another element could be in detection of terrorists maybe some kind of intelligence agency, different terrorists could have differing resistance to detection.
Examples:
Nationalist/Resistance Terror - Various possible options here, perhaps more common after taking a country. Strong resources, Low resistance to detection.
Possible effects:
Access to semi & auto weapons as such they can induce military casualties (Wounded & Dead).
Targets key infrastructure, damages transportation, factories for example.
Civilian casualties lower.
Racial/Religious Terror - Various fundamentalist organisations. Moderate resources, Moderate detection resistance.
Possible effects:
Mainly targets civilians, large numbers of civilian casualties and damage to capitals & cities in particular with some damage in smaller settlements.
Lone Wolf Terror - General group includes general nutcases. Lower resources, High detection difficulty, lack of associates makes them hard to identify and track.
Possible effects:
Again targets civilians especially particularly easy targets such as schools or hospitals.
I am sure people could come up with other suggestions too.