All through my childhood (1950's-60's) I never went to a hobby shop that was primarily a train store and those hobby shops that I did get to visit never had a dealer display - just racks of Lionel boxes in shelving behind the counter and trains on display in cases below the counter. The only places that had dealer displays were places that typically only offered trains for sale around the holiday season.
A hardware store in Minneapolis, Minnesota whose name I've forgotten, had one of the smaller dealer displays off to the right hand side as you entered through the front door. It was positioned so that you could see it from the street. The counters for display and the shelving for product were to one side.
Payless Department Store - Sacramento, California - would position one of the larger displays in the center of the toy section during Christmas. All of the product was in help-yourself shelving off to the right hand side of the display (you came in from the front, walked back to the toy section, found the display (shorter side facing the store front, longer side facing an isle - product shelving on the right-hand long side)
Rhodes Department Store - Sacramento, California - pretty much the same set up as Payless except the shelving did not have as many courses as Payless.
Joe the Motorist Friend - State College, Pa. - Medium sized display all the way at the back of the store - as above Christmas time only. They had the same display and brought it out several years running - it began to look a little shopworn towards the end. Banner above the display announcing Lionel Trains. Product on shelving on either side of the display - the display and shelving were portable and all of it went back into their storeroom after the holidays.
I realize these are only word pictures but perhaps they will give you some ideas.
