If bunny wasn’t on a relentless hunt for his valentine treat, you could probably see the craft supplies better, but I’m not messing with those teeth. It doesn’t matter too much though, because all you need for this project is your valentine postcard design, a printed template of the card, cutaway stabilizer, tear-away stabilizer, an empty bobbin to wind, and some fabric.
For the fabric, especially for the back piece, I would recommend a smooth, light fabric with a tight weave. You want to be able to write on your card, so I’d avoid fabrics with too much texture or grain. Muslin or quilter’s cotton works pretty well. The fabric you use on the front can be anything, but keep in mind you don’t want to make your card too thick or bulky.