It's a bit of a tradition in the children's book industry that illustrators often send in post to their publishers with a little something drawn on the front of the envelopes they use. I first became aware of this tradition when I worked at Scholastic and Alison Green, who's published Axel Scheffler's and Julia Donnaldson's picture books over the years, showed me her extensive Axel Scheffler envelope collection. I was indeed wide eye'd with envy. Here are a few envelopes from other illustrators.

Axel Scheffler

Binette Schroader

David Mckee

Emma Chichester-Clark

Fiona Moodie

Peter Coplans

Posy Simmonds

Sara Fanelli

Satoshi Kitamura

Susanne Varley

Tony Ross