Now that I think about it, you are right in that the library would probably not allow anything to be sold in it.
We could go the hotel route, but would a hotel room work?
To me it seems like it could be a little crowded,
(and you are right, the library rooms are not huge, but I think if we got 2 of them together we would have a decent room)
and there is another problem with the hotel idea.
It doesn't seem very "open" like anyone off the street could come in and see our dioramas.
The library is perfect in that aspect.