The quilt rack is a good idea. Another option would be if you have any wall space & can affix a piece of felt/batting/thin wool blanket to the wall, you could pin quilts to the "design wall". Don't even need to necessarily have the entire quilt showing for all of them. You could layer them so they just show 4" or so (1 row) of each design & let people flip through them (make sure to put some PinMors or pencil erasers on the back of your pins or you will be picking up pins & quilts all day long).
When our guild had our bi-annual show last year, they pinned the table runners to moveable walls (the foamy cubicle walls often found in offices). It looked really nice ... but of course, we have over 80 people in our guild with almost 200 entries & we charged $8/day or $10 for 2 days admission so we could afford to put up fancy displays like that. I'm sure whatever you do will look beautiful and people will enjoy all the hard work everyone put into their quilts.