The host metadata, as it shows up in the macOS Finder/open dialogs/etc, is configurable by having your host publish an mDNS _device-info._tcp service record. You can publish a display name (as arbitrary unicode), an icon (as a machine model name), etc.
I'm guessing Apple figured that if they made the default icon insulting, that might incense Microsoft into building mDNS support into their SMB stack, just in order to use it to broadcast that _device-info service, to make Microsoft SMB present more professionally on macOS clients.
Sadly, Microsoft never bothered. But at least I get to use it to make my Linux homeserver look like an Xserve! (See https://www.tumfatig.net/20170607/let-mac-os-auto-discover-y...)
(Though, sadly, this exact combination of mDNS-announcing-SMB is what is broken in the newest macOS, so I can't recommend you follow the above guide right now. Maybe we'll get support for this back in a few releases...)
I don't know, I find it funny/charming and I'd be sad if Apple got rid of it. It's something of an easter egg—you can't tell that it's a BSOD unless you open the QuickLook or Get Info window (or set your Sidebar Icon Size to "Large").
Agreed. And then there's that extremely childish "Windows 95 blue screen" icon representing SMB shares... Really professional.