Thank you for putting together a lot of ideas for enrichment of the flock. I think there's a lot of ideas that I can use in redesigning our coop and run right now. I definitely will be doing the tire dust bath, swing and outdoor perches/roosts.
As another idea, I am also going to try to have beds or pots of herbs in the warmer months covered with hardware cloth about two inches above the dirt so that the herbs can grow through for the chickens to forage on but the chickens will not be able to completely eat the plant or dig up it's roots so it can keep growing back.
I would proceed with caution on some things like old pumpkins and CDs. Salmonella is something that should be a real concern, and a jack-o-lantern left out for days or even weeks could be harboring such an illness. As for CDs, I've broken a CD before by accident, and it can leave some sharp edges. A good wind can smash a hanging CD into a branch, wall, or fence and leave sharp edges laying in the run.
Even though I no longer need the obstacles for integration purposes the chickens seem to like having some clutter in the run. Not only does it continue to provide hiding spots for lower ranked birds but I find that the chickens just seem to like having things to explore around.