So far SteveH and Macybaby have the best display options here that I've seen.
I wouldn't really say mine are on display. Between my daughter and I we currently have 3 cabinet machines that we use in the LR. When my treadle machines are done being restored I'll have to decide which machines go in the LR at that time. 3 is about maximum in that space. My Singer 27 from kateluvstoquilt is too pretty not to display, it's going in the LR for sure.
It seems that I always find cabinet machines that I like and never portables. I'm trying to focus on portables just because of the space issue.
If (when) I find a good handcrank machine I'll put it in the LR too.
I have an English made bookshelf from around 1900 to 1920 that needs the glass replaced on one side. When I'm done with that project it will go in our 3rd BR and will hold a couple portable machines as well as my wife's cookbooks.
I saw pictures of a storefront that has glass shelves in the windows full of antique machines in another forum. I don't remember the name of the store though.
Rodney