There’s a potential class of card for the game that you could call “oracles”: cards with a blank flipside, that are meant to be shuffled and drawn to generate a random result. Here’s a few sample oracles.
When a character must meet a challenge, a player might draw from a dozen or so cards. Half of them give you a hit to meet challenges, and spell out why or how you do so, e.g. “just barely” or “with style”. The other half can provoke interesting or random failure conditions, e.g. “other side gets there first”. This is similar in spirit to the Deck of Fate, and can substitute for dice.
You can add 6-8 cards representing core human emotions: Joy, Surprise, Anger, Fear, Disgust, and Sorrow. Draw one of these to set the tone of an interaction with an NPC, a new discovery in the world, and so on.
I had a random table for Discoveries in Grand Adventure: the nature of the thing (Mundane Place, Exotic Place, Object, Artifact, Creature, or Event) and an objective (Arrive, Escape, Solve, Obfuscate, Improve/Fix, and Break/Harm). For example, you might draw “Object” and “Escape” - the PCs have a MacGuffin they need to get safely away. Optionally, you can draw an Emotion card at the same time - a Creature you must Harm that evokes Sorrow has a tragic story, like a wounded beast that has turned man-eater and must be put down (or otherwise dealt with) before it lashes out at anyone else.
Grand Adventure included 20 sample twists, including Betrayal!, Forgot Something!, Made It Worse!, Pinned!, and more. These might be interesting one-off cards to draw when you need a random event that forces a challenge on one or more PCs.