There is limited scope for ghost signs on Venice's streets, simply because most streets are so narrow and their buildings are crammed in so tightly that highly-visible gable ends are uncommon. Some businesses responded creatively, by placing mosaic adverts on the pavements.
My first, and very favourite, find was this wonderful travel agency mosaic complete with aeroplanes. SAIET were established in 1952 and still operate in the Veneto, offering freight shipping services by road, boat and air. 71G San Marco, at the outer corner of St Mark's Square, is now an art gallery.
Another travel agency (now apparently gone) and American Express remind the pedestrian that they are in the tourist heart of the city, near St Mark's Square.
AmEx travellers' cheques cashed, food and entertainment were waiting nearby. The Martini night club seems to have disappeared. There is still a Taverna dei Dogi, although it may not be the same one.
Further north, in Cannaregio, the casino also seeks to tempt tourists to part company with their holiday money.
Ironically, the most restrained sign is advertising a mosaic-maker in Dorsoduro. However, their Grand Canal facade does a better job of showcasing their wares. Salviati himself was a lawyer, not a glassmaker, but he founded the company in 1859 alongside craftsman Lorenzo Radi and contributed a talent for marketing. (Their London showroom on Regent Street is now an Apple Store but still displays beautiful mosaics on its facade, too.)
I haven't been able to find much information about this form of pavement advertising. If anyone knows of its history, it would be wonderful to learn more!