That might a very long shot, but why not having stickers with the following designs:
* most important PEPs: we can highlight PEPs which have shaped the Python we have today
* modules included in the standard library (e.g.: "import os", "import collections", etc..):
* sentences from PEP20: these might be horizontal stickers
In all cases we have a consistent amount of different stickers which would be fun to collect them all :)
Unfortunately I'm not a designer so I don't have a clue on how to design them, just wanted to share my ideas.
Cheers