Postcards are something most tend to keep.  It is one thing I do and I am so glad I did.
I compiled for Miss M a medium sized envelope titled "People, Places, Art and Interesting Things" (as if the later aren't interesting) for the last long over seas journey we made.
Inside contained postcards from friends, family, adventures prior to family, art exhibits, museums, historical monuments...etc etc.  In total about thirty two-
Miss M loved opening the envelope...and maybe interested in each post card...but, the different writing on the back and the colors that each post card contained held her captive for about...twenty five minutes...we did go back to them again later in the flight.  Every minute counts keeping the one you love the most happy, quiet and ready for the next 8 hours.
(image by J.Whipple)