This seems like a good idea, but I hope it doesn't stop the recent tradition of yarn-bombing[0] the postboxes[1][2]. The ones near me are really creative, change with seasons & national holidays, and just add a bit of British whimsy to day-to-day life.
(Looks like there's already some articles on this angle [3]!)
[0] https://en.wikipedia.org/wiki/Yarn_bombing
[1] https://en.wikipedia.org/wiki/Post_box_topper
[2] https://www.bbc.co.uk/news/uk-england-derbyshire-63833983