The Chaos Scar is a good sandbox, with a lot of low-level adventures and a few ones that go up to Paragon Tier. You can create a whole campaign with those adventures, with a tie to the Nentir Vale, so you can exploit this to steal stuff from the general 4e sources. If you have access to it, "Keep of the Borderlands: A season of serpents" is a good way to start a campaign in the Chaos Scar.