I've been wanting to do UR control for a while now. I have that deck, and it's solid (does pretty well at my local FNM), but I wanted to spice it up a bit. I decided to try and add some green, partly because Khans of Tarkir is coming and I'm feeling Temur (although Jeskai - URW is a close second), but also because I think green adds some depth to UR.
This is a control deck without Supreme Verdict. That means you have to absolutely optimize every single spell you play to get as much value (via card advantage or otherwise) as you can. Kill that creature that's about to get enchanted, for example. However, you also should have a safe early game since Courser of Kruphix and Sylvan Caryatid are available, thus giving aggro decks even more of a headache facing you.
You also can handle larger threats with Kiora, Turn // Burn, Ground Assault, and any of your counterspells. If Keranos is on the field, he also effectively makes every creature 3 less toughness than it currently is. So if that 5/5 polukranos is giving you issues, then a Keranos bolt and a Magma Jet will solve the problem.
Keranos is also a win-condition, offering plenty of Lightning Bolts to your opponents' face. Xenagos, the Reveler is a experiment for me; really the only thing he does is make 2/2 creatures, but over time that will eventually overwhelm your opponent, or just provide blockers. Useful either way.
Considered Cards:
Jace's Ingenuity - I'm not liking the lack of card draw in this deck. The playset of Jace's should help, along with the occasional Kiora draw, but if it becomes a problem then this card will likely go in.
Perilous Vault - My UR control looks a lot like this deck, but less permanents. Same amount of Jace's and Keranos', but no other nonland permanents. Thus a Perilous Vault would fit in that deck. In this one, however, I would lose any of my Planeswalkers, Coursers/Caryatids, and so forth as well. Not as worth it. Still, I like boardwipes, so I'll be keeping it in mind.
Polukranos - A four drop 5/5 that can get bigger is nothing to sneeze at, not even in a control deck. I mean, he's also removal - I just can't abuse Nykthos mana for it. I decided to play him in side for aggro decks. Of these considered cards, he's least likely to go into mainboard, but I like him in the side.