Venice is an awesome place for Photohraphy. I found that the best timing to go is when it is off season - so around late January/February. While it was freezing cold, the city was empty. I mean, of course the touristic places were relatively full, but rumor has it that Venice is usually so crowded that you can not move through the masses when going through all the small streets.
Anyway, it was a pleasure to pace around the empty tiny streets and take pictures at every bridge. Do it, go there! Off season!