In one of the groups I belong to we had to choose a theme and alter an Altoid tin to fit that theme. There are five people in my group. Here are their mini's for their tins. Each one is 2" x 3 1/4"; just a little smaller than an ATC.
Hope's owl theme:Marilyn's children theme:
Astrid's bird theme (I love working with birds...):
Renee's Zetti theme:
AND mine! I love Zetti too; had to make one for myself!