I make gift cards from the old greeting cards too ..... fold as you like, and then line up with my quilting rulers and run the rotary cutter along. Nice and straight and square!
Sometimes I use the picture ... and sometimes I use the verse on the inside as the front of the new gift card.
I'm able to make teeny-tiny cards, to some fair sized ones.
I always have far more made, than the gifts I need them for. They give me lots of choices, so I can personalize it to the person who will receive it.