There's a system the local art/history museum uses to store and display its
collection of paintings for rent.  It is home made.  The basic unit is a
panel such as a sheet of plywood with something like 1x4s or 1x3s around the
edges to make a very shallow box.  The panel is stood up vertically and the
paintings are attached to it.  Then a bunch of these panels are set up side-
by-side with pieces of lumber between at top and bottom to separate them.
The final touch is that each panel has a narrow (maybe a foot wide) wing
attached to the back by hinges.  There is a handle on the 1x4 edge of the
panel that faces out into the room.  So when you want to look at the
paintings in a panel you pull on the handle to slide the panel out into the
room.  Then when you get it all the way out of its slot, except for the wing,
you can turn it sideways on the hinges to get a better view of the art.
The wing is still between the separators so the panel can't fall over.
I imagine there are stops so you can't pull a panel out too far and have
the wing come out of the separators; but I haven't tried to pull one out
too far.  They probably have domes or rollers or casters under the panels
to make them easier to pull out; tho when I tried it it was still rather
hard (maybe no casters, or maybe poor quality casters).
 
So if you have a space maybe 8 feet high and five feet wide and five
feet deep you just nail the separator boards to the floor and ceiling,
make the panels from 4x8 sheets of plywood, make the wings a foot wide
by 8 feet high, and you could get twelve or fifteen of these panels in
a space five feet wide.