|WHITE STAMPING WITH PENCILS|
Select a fairly solid stamp, and stamp the image using white ink. When the ink has dried (if you want to be sure, just whizz over it with a craft heat gun for a few seconds), colour on top with coloured pencils.
As you can see - super simple, but quite effective. You end up with a gentle chalk-boardy effect.
I deliberately haven't added a greeting as you could use this card for many occasions.