While I'm sure there are gondoliers out there who believe there's only one right way to cover a gondola, the reality is that there are so many variations out there, I could post different examples until people sent me hate mail.
Nevertheless, I am sure there are folks that check in here who would find a few images of canvas interesting.
I also like this one for aesthetic reasons - the striped poles and old bricks help make the shot all the more interesting.
This photo was taken from the vaporetto near the San Toma traghetto. Some guys just settle for "two triangles" and wrap their seats and parecio with a tarp or extra canvas. The owner of this gondola put a little more thought into the equation, and came up with what you see here.