Ashnod Reanimator

Ramp

Of course, the Dan Frazier mana rocks.  I should add though, grixis is one of the color combinations where you can get all of the mana rocks you need in cheaper forms than the Dan Frazier secret lair provides.  Wayfarer's Bauble & Mind Stone pair particularly well with Ashnod's ability if you can wait to activate their ability until you have Ashnod in play.

Fill The Hand & The Yard

This section is the main reason I've chosen to add blue to a reanimator deck instead of just opting for a commander like Chainer, Nightmare Adept.  I love cards like Psychic Frog, Breathstealer's Crypt, Frantic Search, & Fact or Fiction to help put juicy reanimation targets into the yard!  With this commander in particular, you can get free card draw by playing Mishra's & Urza's Baubles which are both effective and good in this situation and you benefit from the other great blue draw spells such as Rhystic Study.  Fblthp is a decent draw engine if you are able to reanimate him or make copies with something like Feldon and you never feel bad sacrificing the poor lost fella to Yawgmoth or any of our other sac outlets.  

Lieutenants

Lazav can become a copy of any of Ashnod's Understudies from below in the yard and return another creature and himself to the battlefield while also having the ability to become literally any creature in the graveyard and give it pseudo haste.  Emry will enter and mill us while typically only costing one mana.  There are enough good targets that are artifacts that we can cast with her activated ability such as the baubles for free, or bring back a Wayfarer's Baulble or Mind Stone that we may have activated early game.  Feldon can make copies of anything in the yard to use for a turn, again potentially reanimating an Understudy.  Chainer will give all of our reanimation targets haste which I feel is one of the top 5 best keywords in commander.  And Yawgmoth is an incredible card that we can double up on his draw ability while putting double -1/-1 counters on our opponents creatures.  Yawgmoth is just brutal.  Any of these legendary creatures could command their own powerful deck but I couldn't resist combining all of them into one deck. 

Ashnod's Understudies

These are some of the cards that will benefit from Ashnod's ability the best as it will allow us to return two targets from the yard with one of them being the necromancer itself if we choose.  We also run plenty of artifacts that we would want to reanimate, whether that be Ichor Wellspring or Wurmcoil Engine to make a Goblin Welder fantastic.  helm of Possession is an underplayed card that will allow us to gain control of not one, but two of our opponents creatures!  I can see this being a removal target that we will need to bring back with our Goblin Welder as well.  

Targets

All of these targets should provide us with value in some way.  Aura Thief can be reanimated at instant speed with a necromancer to surprise an opponent with a block, also the foil is amazing.  Thalakos Deceiver will allow us to gain control of two of our opponents best creatures unless they can block a creature with shadow, which is highly unlikely all of your opponents can do at the same time.  Solemn Simulacrum dies great and enters great providing us with incremental advantage throughout the course of a game.  hellkite Tyrant, Etali, and Lord of the Void will provide us with card advantage.  Tidespout Tyrant will reward us for simply playing cards and fly in for damage.  Platinum Angel is a target that must be answered that we can reanimate to provide a constant thorn in our opponents side.  Noxious Gearhulk gives us an artifact and creature to sacrifice if need be to activate abilities and has a great ability when entering the battlefield on an evasive body.  

Other Synergy

Stifle is the other big reason I like to include blue in a reanimator or graveyard strategy deck.  Every black deck that sits at a table should be running, at the very least, a Bojuka Bog and the only way to get around this effect is a Stifle.  There are plenty of other cards that Stifle will stop as an opponent tries to get rid of your graveyard and I think Stifle is one of the only ways available to us to counter these effects.  Soul-Guide Lantern, Executioner's Capsule, & Stronghold Assassin will all have their effects doubled by Ashnod for extra value and Anger gives that haste I value so much.  Haste will allow you to swing in immediately for benefit with an Etali, Lord of the Void, Hellkite Tyrant, or Thalakos Deceiver without giving your opponents a turn cycle to respond to them.