A previous GM ad a player built a card mage once upon a time, inspired by cards in the Amber books and the RoleMaster Tarot Mage. Here's what I can remember from the days when AD&D reigned...
His cards had to be in contact for a non-instant spell to continue, so he often tucked them into arm bracers.
He could make new cards, given time. Cards could duplicate any spell, but needed an illustration. Creating a card cost spell points as well as time & materials.
I think he had fewer spell points per day than normal, but points were spent to create cards as well.
He could channel normal mana through them (spell points), or there was an option to use the points infused in the card to cast but this destroyed the card.
There was always a slight chance of card burnout.
Characters were aboard a ship. Spell cards are resistant to physical damage (think pigment inks on rag cardstock) but they could be damaged. If damaged beyond use, the spell points infused in the card would get loose, raw mana tends to make a mess...
The GM worked out a starting deck with the player, who used old Magic: the Gathering cards for props... and ran spells much like playing MtG. (fireball with variable damage, for example).
If I was doing it now for pathfinder/3.x, I would reread and consider the magical scroll rules to patch in wherever inspiration and flavor don't quite cover it.
Have fun building!
