So I have my DIY invitations good to go, but the envelope is woefully unadorned. What to do? You got it: put a bird on it. I have been learning that a cute collection of stamps is really useful for jazzing things up. They're especially useful if, like me, you have no fine motor skills.
The only drawback is it's a wee bit time consuming, but it's fairly rote so you can do it while watching TV or listening to KWAVE. I was cheap and only bought a tiny acrylic base for the fancy new stamps, so I had to do each one separately, even if it was in the same ink color. Moral of the story: you can save money or time.
Add a mailing label in a cute font & color plus a pretty stamp, and you are golden.