I followed a link to a fantastic New York Times article that someone posted on Facebook today. The article talks about "pop-up galleries", which are essentially temporary art galleries created in empty shop spaces. I have heard of an artist here and there negotiating some retail windows for a week or two, but didn't realize creating temporary galleries had actually become so common that they have a term for them!
With ecomomic times the way they are and about a zillion empty retail spaces out there, it makes sense to try to negotiate an agreement with a few forward thinking landlords. It's certainly something I am going to look in to!