Can you explain what you mean in Fate Cards? What will it purpose with those cards? Will it be an oracle deck, a tarot deck, a lenormand deck, self help deck, etc?
You can use as many cards you like if it is an oracle or self help deck since usually a tarot deck contains 78 cards or 79 (the happy squirrel) and the lenormand contains 36 cards (no more no less).
You're the artist, so you can make it anything you want it to be. When you mean how you will make it I'll assume you will be making it while using card stocks since you did mention cards.
Before making your cards I'll recommend searching up those types of decks that I mention as well look up at cardstock. I think it will be your best interest in doing your research before making your deck. That is what I did before I made my lenormand deck.
I used game system blank cardstock and drew my pictures using sharpies.