Concept: Every magician, as a rite of passage from layman to cardician, receives a blank deck of cards which he can fill / infuse as he wants.
You can think of this as if it is an inventory, like the sorts you have in a game.
For example:
If you take a glass of water (or any other object) and put it inside the blank card, an illustration of the glass will appear on the card alongside with a suit and color. This glass can be at any time taken back into reality by the magician, but the illustration will stay, allowing the magician for countless uses of this power (summoning a glass of water) or for a 1-time use of this power (depending on how you want to develop the storyline).
One can also infuse his card with a taste. If it is a taste, then one has to rip from the card and eat it in order to taste. Disclaimer: this should not replace a regular healthy diet.
Elements can be introduced in the cards: if you burn a blank card, fire will appear on it, allowing the magician to summon a flame equal to the one he used to burn the card with. If you introduce the card inside an ocean, it won't suck the ocean. But, if a tsunami is to come towards you and you hold the card up, then the wave will go in the card.
Theme: Superhero story, nuvella, patter.