Street Wraith seems weak to me. Your uncommon slots are supposed to be really strong points for your deck. He's really only a cantip that loads the grave. I guess with Tortured Existence he's cute, but not worth it imo. Maybe up the Wonder/Psychatog count? Maybe 1 Lightning Grieves for your finisher Pyschatog?
Since you're running a dredge deck, you graveyard should get to a decent size most games. How about Rune Snag over Mana Leak--it'll usually be stronger.
I've found that Ravnica Karoos can really strengthen a two-color Peasant deck. How about -2 Island -2 Swamp +4 Dimir Aqueduct. They may seem slow, but they only slow you down the turn you drop them. They also help when you miss a later land drop. I think they're worth testing.
Diabolic Edict is very good, but how about some targeted removal? Rend Flesh is

more than Edict, but it can serve as pinpoint removal (it hits about 99% of all creatures in the format)l. Maybe -1/2 Edict for +1/2 Rend Flesh.
Brainstorm always seemed underwhelming in Peasant. What about Accumulated Knowledge? It generates more card advantage, and using dredge you can quickly cheat it up to 3/4 cards. I really like AK in this spot.
Overall, I think it is a cool idea.