This evening I've played around a bit with the Sticker Constructor Specification and its template, and this is the result:

Now I just have to:

* find somebody in Europe who prints good stickers and doesn't require illustrator (or other proprietary software) to submit files for non-rectangular shapes
* find out which Debian team I should contact to submit the files so that they can be used by everybody interested.

But neither will happen today, nor probably tomorrow, because lazy O:-)

Edit: now that I'm awake I realized I forgot to thank @Enrico Zini Zini and MadameZou for their help in combining my two proposals in a better design.

Source svg