Lately, I've been considering doing this. Kind of like a postcard-style greeting card; in an envelope, but a front and back instead of a folding card.
If you make it postcard style, the recipients see the pretty front when they pull it out, and then they just flip it over to see a little coordinating decoration, stamped sentiment and/or handwritten message.
I'm just starting to feel like a traditional style card isn't really that sensible.
I'm curious what you all think