Let me see some stamps that are interesting, amusing, or pretty, I asked the nice postal clerk. Among the 3 (yawn) choices she gave me, was this monument to governmental bloat:
Posters of the WPA.
Now, there is probably some historic significance to the program, yada yada, but nothing I'd call amusing or cute.
Then I saw THIS:
And, voila! The choice was made for me. Even the USPS is a fan of Field Day. This proves it. It has its own stamp.
Keep sending letters, groovy friends. They become increasingly valuable with each generation.