What's your opinion on dungeons?
If it some random generated aspect, then add it a similar taste of Daggerfall.
If it about adding many unique items, handplaced, then one should look closer to Morrowind.
If its about a bit of history and story to the place, then lean toward to Fallout 3.
I love it if somehow, all three above is added together.
Since the game may or may not be in Skyrim, I think it would be interesting to see your character start off as a prisoner in the settlement of Raven Rock on Solstheim, and make way west towards skyrim. The town could be the dungeon tutorial, as you could start underground where all the ebony ore was/is and make your way above ground, and to a dock.
From there you sneak your way onto a boat that just so happens to be sailing to Skyrim. That could open up the possibilty to revisit the island in an expansion as well. Solstheim would be a much different place, with the dunmer displacement and all.
Naw. I think they should stop with the prison intro, its a bit too forceful for background making for toon (I don't like it to happen like Oblivion again). I view at least it should be in tasted of more opening, like http://www.tesnexus.com/downloads/file.php?id=11495 mod, or a ship wreak similar to Daggerfall, or maybe the PC is traveling with a caravan. At least with these, the PC does not start out as a dumb convict.
And my own suggesting, I like to see some buttom mapping. For example, the key M will open Map and key J open Journal and etc. Also, when selecting things in the inventory/container, I would like to at least hold shift or Ctrl to pick one item or all items without the need to go to that "how much" menu.