Ok I’ve been having a look at this - there are a lot of models recognised in MacOS Catalina, and to be honest I find the RackMac one a bit ugly, so here are some of the options available and their string name:
Previous versions of Samba (on Stretch) use the Windows (BSOD) icon at the bottom right but I think we can do better than that. 
My opinion is the Macmini icon is probably the most apt as it looks most like a Vero and a Mac Mini is often used as a file server, so it sort of fits, and it will stand out from other Windows PC’s on the network.
But I’d be interested to hear what other people think especially @sam_nazarko as to which icon we go with… as far as I’m aware this setting only affects the icon displayed and has no functional effect.