For more ideas, go here: http://www.ldrmagazine.com/blog/2015/01/22/put-inside-open-letters/
I'm in the process of doing some Open When cards for my long distance boyfriend. Here are the titles of each card I'm making. I also decided to do one with the answers to some of the puzzles I'm putting in a couple of them. (:
Ideas for the Open When... Envelopes
Willkommen in meiner kleinen Bastelwelt: Ein Wenn-Buch zum Geburtstag
Wenn du mal einen KLEINEN URLAUB brauchst ...
"violin bow laying on vintage music sheets"