My boyfriend and I have been working on creating an EDH deck based around Kaalia of the Vast as the Commander.
What we have so far is this:
http://deckbox.org/sets/301359

It just doesn't seem right yet.

I have been thinking about building a Kaalia deck too.

What constraints are you working under? I would cut the urza's lands (too vulnerable), slumbering dragon & dragon hatchling, kingpin's pet, reiver demon, and some other stuff, but not sure what you'd want to replace them with.

No constraints. We play casually with friends so there is no concern about Format, or banned lists, or any such thing. If its a card we own and we like it we play with it.

Kaalia decks usually focus on cheating into play the biggest, baddest, fattest dudes in the game, so right away you can probably safely cut anything that isn't big or bad enough. I'd also be looking for ways to protect Kaalia herself, and ways to get just the guys I need into my hand.

I'd make the same cuts as Nighthawk, plus:
- Serra Avenger
- Furnace Whelp
- Lightkeeper of Emeria
- Dread Cacodemon

and start adding things like:
+ Griselbrand
+ Ryusei, the Falling Star
+ Kokusho, the whatever Star
+ Dragon Mage
+ Demonic Tutor
+ Lightning Greaves
+ Swiftfoot Boots
+ Enlightened Tutor
+ Necropotence

I agree with Loot Pinata accept for Necropotence, while the card is absolutely amazing to get BBB in a 3 color deck is pretty difficult to accomplish unless you're willing to drop some serious cash on lands, however if your games are fairly slow it could be a good option I'd guess that Phyrexian Arena would be better in this deck, but that might just be me.

LootPinata wrote: and start adding things like:
+ Griselbrand
+ Ryusei, the Falling Star
+ Kokusho, the whatever Star
+ Dragon Mage
+ Demonic Tutor
+ Lightning Greaves
+ Swiftfoot Boots
+ Enlightened Tutor
+ Necropotence

Definitely the Kokusho. Griselbrand is generally banned, so keep that in mind if you ever want to play with another playgroup. If you do want to play with him, enjoy getting him into play and drawing a big chunk of your deck.

Bloodgift Demon and Phyrexian Arena are good for drawing cards as well.

Good call on Bloodgift, that's certainly a better option than the arena, I didn't even think of that guy

Another thing to consider would be the original Rakdos, Rakdos the Defiler if you can find one, the way that his ability works when he is brought in with Kaalia he doesn't actually attack, he just enters the battlefield already attacking therefore if he tramples through (And let's face it, he's huge) your opponent will have to sacrifice half of their stuff and as long as you don't attack again you won't have to do the same

I will echo the above opinions of cut the low CMC dragon/angels/demons. You want everything that comes into play to be somewhat game-changing. Dragon Whelp changes nothing when it hits the field.

Also, I notice a lack of mana-rocks. You've got enough land, but you still need some rocks to help with color fixing and such. You'll probably want all three Signets for your colors (Boros, Orzhov, and Rakdos) to fix your mana, also Sol Ring is never a bad call.