I really like these fabric heart bookmarks from mmmcrafts. Wouldn’t they be cute tucked inside a thank-you note or as DIY favors? You can check out the full tutorial here.
And check out these sweet fabric flower cards also from mmmcrafts. These would make pretty shower invites, or thank-you notes. Read the tutorial here.
And last, but not least, aren’t these fabric heart cards from The Purl Bee lovely? You could modify them and use them as escort cards, or simply keep them the way they are and use them as thank-you notes. Go here for the complete instructions.