I've done the Butterfield Loop. I believe there is no camping inside Devil's Den State Park except for the campground, but you can camp almost anywhere in the national forest, following whatever rules they have about distance from trail, water, etc. The rangers at the park or the forest service should be able to tell you for sure. As I recall, there were a couple of established campsites along the trail in the national forest, but you don't have to use them. If you start at the park, you will need to get a (free) permit to park your car overnight.

I think the Shores Lake loop is entirely national forest, so you should be able to camp almost anywhere.