This idea is almost so obvious, that it nearly makes you angry that you did not come up with something similar yourself.
Angkasa Pura (company operating Indonesian airports) in conjunction with Indonesian tourism board launched a series of small paper packages showing the stories and designs behind the humble Indonesian coin:
When you open them up, they work as a display stand where you can fit a leftover coin from your trip to Indonesia. These could be picked up for free in Indonesia´s airport:
Insight: When you are traveling abroad, you will have bunch of foreign coins you cannot really use anywhere. What if you would turn something worthless into something worth remembering?