Shrines with mosaics inside of them aren't that common, but there are a few of them around Venice. I posted a few a while back, and here's another one I found last year.
This one's in Cannaregio, and the mosaic is a copy of a sacred image of Madonna Addolorata (Our Lady of Sorrows) that can be found in the nearby church of San Marcuola. The owner of the house where the shrine is (on Calle Lombardo) commissioned the mosaic from the Orsoni family in 1970. The Orsoni are well-known mosaic artists who offer classes and also have a B&B in Venice. On one of the Venice episodes of her travel show, Samantha Brown took a mosaic class from them, and it looked like a lot of fun.
I wonder what the little padlock hanging beneath the shrine is for? Another note about this shrine - you can see where a graffiti "artist" wrote "Ciao!" on the base but someone has tried to clean it off. Venice has a graffiti problem, for sure, but it's unusual to see graffiti on a street shrine.