Hand drawings possess a certain vitality that works well on cards. I always start with rough pencil sketches and when I'm happy with one, I will copy it, so that I can quickly reproduce it later. You can use a photocopier, a lightbox, or trace against a sunlit window. I use Aquarelle Pencils and water brush for colouring, with a fine, black ink outline once completely dry. Add a small embellishment for dimension or sparkle as the finishing touch.