We've definitely seen embroidered greeting cards around the craftosphere, but I'm really liking this version from Diane at Home Sweet Homemade. She first applied a series of stamped or spattered paint treatments to her cards, and then planned the stitching design. (From there, you poke holes and stitch.)
Bonus: she's using a saltine cracker box for card stock! I think this Greek key stitch design is really elegant, don't you?