There is excellent camping to be found off the road of the NFL. I guess it comes down to how rustic you want it to be and how low or high you want to make your base camp.
Lower, Upper NFL:
Good, primitive campsites off of the bridge on FR23 going over the Muddy River. Driving north from FR90, take the very first left after you cross the Muddy, drive down a gravel road about 50 yards- several feeder roads break off to the left towards the river where you can pick a spot on the sand.
Middle, Upper NFL: Drive up FR90 11-12 miles from Northwoods- FR90 crosses the bridge after a short gravel road section. Most people (including myself) informally call this bridge Lower Falls Bridge despite the fact that Lower Falls is 1 river mile above the bridge. RIGHT after you cross the bridge, theres a turnout to the right that gives you access to Trail#31 which is heavily used by mountain bikers/hikers etc. There's some small clearings between the trail and the river that are well sheltered against wind that blows up and down the canyon this time of year.
Lower Falls Campground: Sure it's a campground- but it has some nice facilities, doesn't attract the type of riffraff Swift Forest camp tends to attract and gives you access to the NFL just below the falls which is a really nice dry fly spot towards the end of the day. Don't forget your sink tip like I did last trip.
Upper, Upper NFL:
Keep going up FR90, going past Lower Falls, Middle & Upper Falls. A bridge crosses Quartz Creek on river left and holds a few nice spots with easy access to the creek and the river.