http://planetelderscrolls.gamespy.com Here are tons of files convertable for civ4 with blender. But be aware of high polycount I just will use files which wont exceed the size of 40Kb, this is still high but better than attaching a whole unit to another just to have another head. Not sure if I understand what you don't understand. With bits I mean attachable nifs like weapons or heads(!) to create new units with them in the nifviewer. If you want create headattachments for playing with the nifviewer remember to delete the animations.