I guess the problem here, to me, is that we have a hard time getting volunteers for anything, especially something like manning a store. I very much like the idea of using this to present what was made by members and creating something that will help actually bring people into the space. of course $25/month may not be the right price and I don't know how big a cube should be. If the maker is making large items I expect they would just put pictures of them in the cube.
If the cubes are all the same size, I don't really see how a large ugly item can get outshine a bunch of well made things. The other issue with consignment, is that there is no drive to get turnover and improvements. With consignment, if it sells, it sells and if not, no one is harmed except the CoG and other people that might do better with the limited number of cubes. This was the problem my wife had when she consigned stuff. She was basically acting like storage for items that didn't sell. The cube rental drives heat to the makers to make stuff that is good enough to sell.
Again, I'm trying to convey that the makers themselves need to be responsible for the works, and minimize the amount of work the CoG and its members have to do. By charging for the cube, the maker will have to worry about how good the quality of stuff is in there. I agree that things may take months to sell, I expect the cubes to be big enough so that each maker could display more than one thing in there.
Maybe to start out, some of the cubes are consigned, and some are rented? This will give a option to people who want to sell when the free, consigned cubes fill up.