My favorite was amiyesiam's triptych art (quote is below). No theme, but wow...did it get creative with each one I made, and to see each one made by others, was creativity at it's best, amazing.
Hoping others can add to it. Back in the day..2010....to the best of my recollection at 4:00 AM.
Gemme...started us out with Passion. Whatever your passion was, kept to a size of 4 x 5 or 6 inches..Most projects were limited to that size, not numbers of sign-ups, for reasons of postage when you get 10 to 15 or 20 of us.

. For me, The more the merrier , because, it is such fun to see what a group of creativity in a postage envelope looks like when opened. Some projects were limited due to complexity, etc.
Themes of "Words", colors, cards, magnets, and whatever you made was with your own creativity, your hobby.
Titles such as Passion, Written Word, Secrets, favorite things, favorite quotes.
We did the color green,
We have made jewelry, and crafts, to the themes...
Spring
Post cards
Photographs
Holiday themes of Halloween, Valentines Day, etc.
Every year we have donated created or fun items (whatever )for a PenPal Thread Basket for the Raffle
and ..the Altoid tins...we did more than one though, like 6 to 10??, for everyone that signed up.(empties provided by the wrangler).
My favorite was amiyesiam's triptych art. It was awesome.