I believe this is now fixed.

I did just refactor some of the code, but everything on my end looks to working. Cards never had the image_url property, only editions.

[
  {
    "name": "Alhammarret, High Arbiter",
    "id": "alhammarret-high-arbiter",
    "url": "https://api.deckbrew.com/mtg/cards/alhammarret-high-arbiter",
    "store_url": "http://store.tcgplayer.com/magic/magic-origins/alhammarret-high-arbiter?partner=DECKBREW",
    "types": [
      "creature"
    ],
    "supertypes": [
      "legendary"
    ],
    "subtypes": [
      "sphinx"
    ],
    "colors": [
      "blue"
    ],
    "cmc": 7,
    "cost": "{5}{U}{U}",
    "text": "Flying\nAs Alhammarret, High Arbiter enters the battlefield, each opponent reveals his or her hand. You choose the name of a nonland card revealed this way.\nYour opponents can't cast spells with the chosen name (as long as this creature is on the battlefield).",
    "power": "5",
    "toughness": "5",
    "formats": {
      "commander": "legal",
      "legacy": "legal",
      "modern": "legal",
      "standard": "legal",
      "vintage": "legal"
    },
    "editions": [
      {
        "set": "Magic Origins",
        "set_id": "ORI",
        "rarity": "rare",
        "artist": "Richard Wright",
        "multiverse_id": 398436,
        "number": "43",
        "layout": "normal",
        "price": {
          "low": 0,
          "median": 0,
          "high": 0
        },
        "url": "https://api.deckbrew.com/mtg/cards?multiverseid=398436",
        "image_url": "https://image.deckbrew.com/mtg/multiverseid/398436.jpg",
        "set_url": "https://api.deckbrew.com/mtg/sets/ORI",
        "store_url": "http://store.tcgplayer.com/magic/magic-origins/alhammarret-high-arbiter?partner=DECKBREW",
        "html_url": "https://deckbrew.com/mtg/cards/398436"
      }
    ]
  },