As the Insurgency in its current form breaks down:
-Almost all(>95%

are Iraqi Nationals
-3 broad groups:
-Islamist, i.e Iraqi nationals who are Muslims and feel the need to efend Iraq from foreign invasion by chrsitians (large majority of insurgents)
-Nationalist (including Ba'athists who were forcibly removed from power, ex-soldiers and Republican guard who had nowhere to go, Iraqis fighting against loss of nationall Sovreignity, probably 2nd largest group)
-Secular (including Communsits driven underground by Saddam)
-Jihadi (including foreign elements, by far the smallest, yet most hyped, group).
The majority of Insurgents consider civilians to not be targets, and try to limit their targeting to Coalition troops, Iraqi Security Forces, Police, and collaborators, all legitimate targets, which are targeted by most groups, though some don't and prefer to attack other militias instead.
Overall, considering the Iraqis have effectively lost their homeland, their national identity, their sovreignity, their stable lives, the semblance of normality from day to day, I can very much empathise if not sympathise with their objectives, and their methods, while sometimes questionable, would be used by their enemies in any case, so ti's a matter of necessity to them.
All in all, I wish them the best of luck in their objectes insofar as removing foreign presence from their soil.