The issue with madness is it takes a few turns to get out a discard engine before you can do much... so the deck does nothing for the first few turns.

That said.

Faithless Looting is the best madness engine in the entire MTG universe. True it is not instant... but it only costs so you can start casting your madness stuff faster. your also can discard Squee, Goblin Nabob, over and over again. then later in the game you can flashback it.

I would remove 2 Zombie Infestation they become redundant, 1 Sedraxis Specter, 3 Extractor Demon I don't really think they are great, 4 Think Twice with madness faithless looting grants card advantage, Jaya Ballard, Task Mage to slow and fragile, 1 Reckless Wurm is a bit high when you also need to pay for a discard, 1 Izzet Charm good but just a bit slower then looting and Axe

add 1 Lightning Axe, 4 Faithless Looting, 2 Merfolk Looter, 3 Grave Scrabbler , 3 Gravecrawler.

Just my opinion.

I like a lot of what you have in here. I stole some ideas from your deck. check out mine Super Budget Madness!!!

+1

If you think the mana base can support then Vexing Sphinx would be killer. 3 CMC for a 4/4 flyer, use him for a few turns as a madness engine and fatty, then he lets you draw a mess of cards to fill you hand up again. I think he is a very strong card for madness!

Merfolk Looter sounds iteresting, in Modern UBR Madness 0.5 i used to Play Looter il-Kor, but I never tried this, because i thought that is too fraile...but block+tap at instant-speed can be quite good

I still don't think that Faithless Looting is a good card:

your initial hand usually has: 2-3 lands, cards that we can discard (WCD) and cards that allows you to discard (ATD) the previous cards

with Faithless looting we need at least 2 WCD, otherwise we have a -1 or -2

And you can't take a mulligan too easily with this deck

I really prefer Tormenting Voice or Izzet Charm

Grave Crawler and Grave Scrabbler(suggested also from Roarmaster) are REALLY Interesting, especially with Zombie Infestation

I really love Vexing Sphinx (tried on previous version Modern UBR Madness 0.5 ), but is not helpul when you are in difficult and need to Have Some strong creatures on the battlefield: 3 turns are the maximum Life expectancy for this adorable-blue-flying-fatty ( never enough)

I have to make some tests

I'm thinking about Gifts Ungiven for WCD research, like Bloodghast, Squee, Goblin Nabob and Grave Crawler

• Gravecrawler

...and Vengeful Pharaoh

Gifts Ungiven is a great idea. Due to it's 4 CMC I would only add a few of them. but the instant speed is sweet! esp. with other instant speed madness engines like Zombie Infestation and Lightning Axe, it lets you do stuff on their turn keeping them guessing and scared and to used your mana mostest wiseliest.