I think you'll do well removing, completely,
Ulamog, The Ceaseless Hunger. He's a good card, but his mana cost and the fact that he actually has to attack I think kinda goes counter to the point you're looking at here.
If I may, Dboe said a lot of good cards there. You may also want to throw in an
Archive Trap. 5 mana to mill 13, and it's free if they crack a fetchland. Can't beat that.
Other really good mill cards are
Mind Funeral (harsh), mindgrind (harsher),
Tome scour.
Hedron crab is a really nice one.
Also, if you wanna have creatures in there, then
Jace's Phantasm is a good one, as is
Consuming Aberration and Wight of Precinct 6. Those last two combo nicely with
Phenax, God of Deception. ALso
Mirko Vosk, Mind Drinker. Another creature I really like in U/B or MonoU mill is
Undead Alchemist.