Its always nice with variety in dungeons. This topic should be focused on dungeon content from a design perspective, to supply those hard working leveldesigners with fresh ideas in case they run out of them.

Things that I would like to see are:
-A scary dungeon. A very dark place (or area in one) that is pitch black and require that the player uses some form of lightsource or suitable spell/potion. It should also come with patrolling monsters so its hard to predict where they are or what direction they will come from.
-A dungeon with a lower and upper area, that needs to be partially flooded so the player can swim to the upper one (and possibly drained again to clear the path to the exit, in case it needs to be reset for later reuse).
-Instead of just walls, deep holes and chasms to add some extra risk and tactical opportunities.
-Underwater tunnels to swim through. Both short and long ones. Could be used to provide alternative routes around wellguarded areas.
-Rooms with a clear purpose; like kitchens, libraries, armories, chapels and bedrooms.

Here's my dungeon design idea.

If you're going to tell me that someone use to live there, then make the dungeon look like someone might actually have lived in it. Not like those Ayleid ruins or old forts in Oblivion.

Different lighting.
Should be some very dark ones requiring a torch or light spell, but not many(from a gameplay viewpoint).
Ice caves should have more ambient light, Im assuming.

Some more varied environmental stuff.
Like FREEZING cold caves that require the use of a warmth potion(supplied by a quest giver or found in the cave)
Or underwater sunken ruins that arnt filled with air and require the use of water breathing.
Maybe some more stuff like that bug cave in Shivering Isles where you had to keep finding the drug to fight off addiction or youre toast.

Edit: Basically adding more gameplay depth and alternatives that arnt based on combat.

All of these suggestions seem great to me. I like that from what we've seen, some of them will have running water in them, which seems good to me too.