Hi! Thanks for your deck, I am a big fan of non-UG madness myself.

Cards to consider, espcially if you feel mana-confident:Violent Eruption as it helps wipe out several smaller creatures and can be nice against aggro decks. Arc Trail works similarly and you can cast it from your hand.

I tried to put together a GR spellshaper madness and even though I have a weak spot for Bola Warrior, it is not very mana-efficient and you cannot use it outside combat, which is the main hinderance of most of your discard outlets. I would suggest Kris Mage who is cheaper to cast and more versatile, especially against aggros. Or you can use her to finish off a bigger creature. Or in the worst Undertaker.

If you are not playing against black and you feel you can muster toghether BB, Gorgon Recluse could be nice.

Any particular reason for not running the Twins of Maurer Estate since you feature them on the deck description?

As for discard outlets, what about Heir of Falkenrath  ^Flip?