For many years already I have bought a Metropolitan Museum of Art Page-A-Day Gallery Calendar, which I keep on my desk at work. I have this year started to save those calendar pages which I think could be used on cards and envelopes. This card to PostMuse is a combination of two pages, and I'm happy with the result.
And this page again looks beautiful on the envelope.
I already have a new calendar bought for next year, so I should have material enough to be used like this. :)