In York there's an old wartime advert for some health supplement painted on the side of a house. It [looked a bit dilapadated](https://i.pinimg.com/originals/9b/6e/6c/9b6e6c3a555dc0669c70e9412bd7ff36.jpg), so in 2012 the council had it [repainted and refreshed](https://pbs.twimg.com/media/A7m4CU6CEAA-T0q.jpg:large). I imagine something similar could be done for these signs.