When we visited London a couple years ago, there seemed to be a post-it war going on high above the city streets. We saw images spanning several windows and sometimes an entire floor. There were cartoon characters and popular sentiments, all displayed through post-its.
Here are two examples of more extreme post-it art.
The Kyoto University of Art and Design created these beautiful post-it art structures that were displayed in their Art Zone - "an experimental space so as to consider how to device structures and systems that would enable art to function as a part of society, and devise them together with artists, particularly young artists themselves."
"Brazilian footwear Company Melissa worked with Post It Note manufacturer 3M to create this amazing opening exhibit at their São Paulo flagship store, using 350,000 coloured Post-it Notes. Over 30,000 of them had spontaneous messages of love written on them from local residents."
(source for all Kyoto School of Art and Design images found here and source for Meliissa store images found here)