´Things to do in Shivering Isles when you´re dead.´
One thing that improved my experience considerably was the no location markers mod. There was much about the environment and I never noticed during the main and side quests. I think I need some make some post mainquest time this summer.
Did you take a look quest pages at
Main Page - UESPWiki ? There might be something there, I don´t know. I kind of rushed the main quests because I lacked time to take my time and play the game.