Some of my storage is under my rolling train table. My wife made alternating brown & camo covers. It is amazing how many people including kids don't notice anything could be there.
I found Pizza Dough boxes at the restaurant supply . They each hold 12 lionel items. Some cookie sheets where the space is a little tighter. All In all I have 25 of the Pizza pans and 6-7 cookie sheets.
Then some kitchen shelf anti-skid in the bottom of the pizza pans. I know, keeping the items on their side is not a good idea unless you have some paper that wont stick to the paint.
I did have to re-inforce the shelves with a 2x4 about every 2- 2 1/2 feet. Those steamers tend to warp the 1/2 plywood shelving otherwise. the table has 6 of the wheels you see in the first picture. I think they are each rated at 500lb/240Kilo or more. About 2x what I need with all the boxes loaded.
My house is 1 story, cement floor, no basement so it works. I wouldn't recommend it on a floor with a basement under it or 2nd story unless the floor was very well made with at least 2 layers of 3/4 ply. It gets heavy in a hurry with a number of steamers.
Running out of storage, isn't that one of the good problems to have?