Quick little idea.
Wouldn't it have been incredible if the End were built out of a mess of the blocks Endermen can pick up? Like they constantly were scavenging during the night and building during the day. And perhaps they could steal more valuable blocks from the player giving you a real reason to visit the End to regain your crap instead of fighting a stuffty "end-game" boss.
Probably could develop the idea bit more but whatever.