As a Customer there is nothing like a good display presentation to be able to see exactly what you are buying, and you may not know you need to buy one until you see it. Today that needs a plastic covered display case, extra cost but solves some problems.
If the stuff is on a wall at the back of the stand for security please make sure descriptions/notices/prices are clear enough to be read by people without their glasses. You don't have time for "can I have a look at that widget, no the one above, no up a bit, how much...."
It would help in some cases to provide a lot more information on the shop's website which is tedious but lower cost and lasts a while. "widget - picture not available " is not much use. Widget, pictured with 3 views square on to some graph paper with a clear dimension, a helpfull description like 'suitable size for 1:32 scale tug of 1950's German design' material of construction and a part number helps a lot more and must result in more orders.