You might be interested to know that you can download some freebies from the U. S. Postal Museum website. This is not to be confused with the U. S. Postal Service. Case in point... when I submitted an envelope to the Graceful Envelope contest a few years ago, I accidentally left off the post office box number in the address. Apparently, the U.S. postal service does not know where the U.S. postal museum is, and they sent the envelope back to me!
Anyway, you can visit the museum website and use their options to make stationary. Rather than make stationary, I put several stamp designs on the page in different sizes and printed those. I also explored all the drop down menus to see what else was there and printed some other things.
Lastly, my post office box rent is due this month, and my postmaster likes it when I decorate my envelope. It's fun for me to surprise her each year.
Go forth and postalize something!