I just came across this plugin and I though it would be neat if it were implemented. It is nothing more than another way to display items. Check it out at this link http://forums.bukkit.org/threads/mech-itemstay-v1-0-create-displays-1-2-5-r1-0.71687/. With this, you could make display cases which I think would be a cool addition to shops.
Yeah! I thought about suggesting this. Instead of having two signs put down a shelf put the item on it and put the sign under it!